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Thread: HP ECU to Holley EFI Analog Style CAN Bus Speedometer 553-120

  1. #1
    Join Date
    Dec 2019
    Port Orchard, WA

    Post HP ECU to Holley EFI Analog Style CAN Bus Speedometer 553-120

    I have determined what it takes to make this speedometer work with the HP ECU. The following posts have a very wordy explanation of the thought process that I had to go through to get there.

    A super short summary is here as follows:

    The speedometer is a Custom Look Speedhut CAN bus gauge. It communicates with the UDS CAN standard (ISO 15763-3, I could be wrong so don't quote this.) The speedometer CAN bus is running at 500Kbit/sec. This is what OBDII, after 2008 for the CARB, uses for the CAN bus and uses Pin 6 and Pin 14 on the SAE J1962 connector as CAN High and CAN low respectively.

    CAN High is wired to the "Tip" of the stereo connector. CAN Low is wired to the "Ring" of the stereo connector.

    The gauge is looking for a hexadecimal response from the ECU/gauge module of 7E8 followed by an 8 byte packet 7 62 F0 27 0 0 ## ## where ## is a hex value between 0 and FF. This empirically seems to correspond to MPH = [decimal value of byte 6 ]* 2.6 + [decimal value of byte 7]*0.01. This at least places the needle on center for all of the graduations on the gauge face except for 0 and 160.

    The HP ECU communicates with their own CAN protocol at 1Mbit/sec. This is why the gauge module is needed to translate and you cannot connect the speedometer directly to the HP CAN bus. NHRA "PRO Stock Electronic Fuel Injection Requirements" documentation contains the public released information on what the protocol is to allow you to see monitor only data from the HP and Dominator ECUs for monitoring and data acquisition purposes.

    For example to get the custom speed I have configured on Input 4 of the HP ECU, I listen for a packet 1E051### (Where ###, the last 3 bits, are different for each ECU) followed by an 8 byte packet where the last 4 bytes contain the data for Input 4.(This is different from what the documentation says input 4 should be, I don't know why.) The calculated speed is the decimal value of the hexadecimal read from the ECU divided by 256.

    To send the data to the speedometer requires setting up a separate CAN bus from the HP CAN bus and the gauge module bus. One 1Mbit/sec CAN bus to the HP ECU and one 500Kbit/sec CAN bus to the speedometer. They can't be connected together through the same CAN bus due to the different speeds.

    The data must be taken from the HP ECU, processed, then sent to the other CAN bus on the speedometer. The gauge module will communicate a continuous 0 MPH signal to the speedometer if you connect the speedometer to the gauge module CAN bus so the speedometer has to be on its very own bus.

    There will be a total of three buses if you have the gauge module: Speedometer bus, gauge module bus and HP ECU bus.

    Original Post:
    I have emailed Holley tech support 3 times at 3 day intervals with no response, so I'm trying here assuming that I'm having browser issues that are not sending the question through the Holley tech support page. I have not received a communication saying to the effect of "We have received a question from you and will get back to you..." like I have with other websites. I'm hoping that Tech support will see this. I have also spent a week searching for the answer and have found very few threads here and on other forums with very similar setups. None have provided an actual answer. Unless someone else has the same setup and has it working and can share what they did, I think that Holley Tech support is my only option. I like things in writing, I will call them eventually if I can't get a response. I unfortunately go to work before they open and get home after they close, except for Saturday I guess. Pasted bellow is what I sent to them. There is more however the tech page had a character limit. You will notice a bit of redundancy in the information provided just in case something wasn't clear:
    The problem:
    The speedometer powers up properly but does not display speed while the gauge display and datalog channel on the laptop are displaying speed.

    Holley software and ECU firmware version is V5 build 30. (My laptop has issues with communications with build 130 so I went back to the newest version that works)

    4 other Holley EFI CAN gauges are connected and function normally. The jumper for daisy chaining to other gauges is installed properly.

    The Speedometer is connected per the included instructions - It is connected to a Holley HP ECU via the Holley EFI Gauge Module part # 554-130. The Gauge module is connected to Pin J1-A15 and switched 12V power per the instructions.

    Also daisy chained together with the Speedometer are the following: Holley EFI 4.5" CAN Tachometer part #553-147, Holley EFI CAN voltage gauge part #553-126, Holley EFI CAN oil pressure gauge part #553-127, and Holley EFI CAN coolant temp gauge part #553-128. All of these gauges read properly when everything is powered up. The speedometer is the first gauge in the daisy chain.

    The Speed sensor is a hall effect sensor connected per the ECU manual's instructions with the +5V sensor line to J1-A26, the sensor ground to J1-A14 and I chose to use sensor signal on J1-A4. J1-A4 is configured on the configuration screen as type “Miles/Hour” with 17 pulses to average and 17 PPROT with 3.87 gear ratio and tire diameter 26.1.

    On the inputs/outputs screen the input Name is “Miles/Hour” (I also tried “158” and “Speed” with an ignition cycle and upload to the ECU). The type is “Digital Speed/Freq.” It shows that ECU pin is J1-A4. The pin map screen shows connector J1 pin A4 with the input type being F “Speed.”

    When spinning the sensor and getting a speed on the “Miles/Hour” Channel in the data log and an indication on the gauge screen of 20 MPH, the speedometer gauge needle stays at 0 MPH. The digital odometer and trip read 0 and the needle sweeps the full gauge face when it is first on.
    Last edited by nicholaspurdy; 12-31-2019 at 02:28 PM. Reason: Add thread summary to beginning

  2. #2
    Join Date
    Dec 2009


    Contact Holley Tech Service (LINK).
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 11.8:1 comp, TFS R-Series FTI ported intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 MT tires.

  3. #3
    Join Date
    Dec 2019
    Port Orchard, WA

    Post Continuing the journey, just can't see how fast I'm getting there.

    I managed to get a Tech on the "Chat" who confirmed what I suspected. I'm not sure if there's a function to keep the transcript of the chat and I didn't think about copying the chat until it had already been terminated.

    Here's a summarized and not word for word of what I learned from the tech after I described the problem that I had.

    Their reply was: Do you have the speed output enabled?

    I replied: The HP does not have transmission control. I don't understand the question.

    Their response was: I'm aware of that. You have to have a speed input to use the CAN Bus and the HP does not have a speed input. The Transmission ICF has to be enabled for the ECU to send out the speed signal on the CAN Bus.

    My response: So if I understand correctly the HP cannot use the CAN Bus Speedometer? Or do I have to enable the Transmission control in the HP and it will trigger something to make it send out the right signal on the CAN Bus?

    Their response: You are correct the Holley EFI CAN Bus Speedometer can not be used with the Holley HP ECU.

    I responded: Then why does the product documentation say that it is designed specifically to work with the Terminator, Sniper, HP and Dominator ECUs?

    Their response: It must be a typo. Someone probably copy and pasted the same information for all of the gauges.

    The ECU has to have a speed input and it has to be enabled by the transmission control to put the signal on the CAN Bus. The HP can not use the transmission control ICF so it can not send out the speed signal.

    I responded: It is an over 3 and a half year old typo then. I must be the first person to have bought one of these gauges to use with a Holley HP ECU.

    Their response: I will try to get them to fix the typo.

    I continued on to at least get more information so I could move on with getting a working speedometer. I'm 1300 dollars in to a complete Holley EFI gauge swap and already permanently altered the dash to install all of these gauges specifically based on the product documentation and instructions. Ironically this all started because I had to replace the speedometer and not any of the other gauges. I like how they looked and decided to make them all match. They do look good in my opinion, especially compared to stock.

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    Part of their response was the only other way for the Speedometer to work was to wire it to a preexisting OBDII because that already has the speed signal in the CAN Bus.

    I'm pre OBDII and there is nothing left of the original car anyway.
    I responded: So if I get some other hardware that I can process the signal from my speed sensor and then send it out on the CAN Bus to the speedometer as a standalone, separate from the other CAN Bus gauges, using the standard for the PID set forth in the ISO J##### I should be able to get it to work.

    Their response: I guess so.

    I responded: Are these Speedhut gauges with your guys logo on them?

    Their response: I think that is correct.

    I responded: Can they just change the firmware to add an option to lock an input pin for a speed input to then allow the ECU to process and put the CAN signal for speed on the CAN Bus the same way that the Dominator does for pin J4-B16 (or B18 I forget, would have to look at the diagram again) when you add the transmission ICF?

    Their response: That would defeat the purpose of having different ECUs that do different things.

    There were a couple more exchanges where I was basically bitching about how it is just software and they were saying sorry that's the way it is they probably could do it but would have to make it more expensive and that would defeat the purpose of having different ECUs.

    They recommended that I try to return it to the place I bought it since I didn't purchase it directly from them. I bought it at a major online supplier whose name is the same as saying you made it to the top of a mountain. Their return policy for electronic items is only for exchange of a broken one (since I already took it out of the box). I wouldn't blame them, it is not their fault that Holley inadvertently made a false advertisement. I also haven't asked a human yet, they probably actually would take the return based on my previous experiences with them. I really want to make this one work so I have a complete set of matching gauges without the GPS option. I also have to get it working or find out if it is broken and exchange it in less than 60 days or I'm just completely out.

    The Holley Tech recommended the GPS version. I'm not interested in the GPS version, plus that means I would be purchasing one more Gauge that I don't need if I can get this one to work.

    If all fails I'm going to just go buy a Speedhut programmable speedometer and calibrate it to match the speed shown in the HP data monitor while feeding the ECU and Speedometer the same speed signal. The speedometer looks identical but without the Holley EFI logo on it. Then I just switch out the gauge faces...

    For anyone interested in the journey, I will post how to either succeed or how to fail at this project kind of as I go. It was maddening to me when I was searching other forums and threads to find something almost there and then they just die or had no explanation to any claimed statements.

    There was enough information between trying to find the end of the internet and looking at the ECU documentation and wiring diagrams to make an educated guess that turned out to be true. However I couldn't actually confirm anything because the guess is based on the absence of information.

    So if there is a Holley employee or someone who can make changes and has managed to hang on reading this far, I have what I believe would be a reasonable recommendation. This is based on me having no knowledge of how the guts of the ECU actually work so please bear with me:

    Add an option in the "Inputs" ICU to toggle a Speed input for the purpose of sending a Speed signal on the CAN Bus to allow all of the ECUs to lock down an input pin and process a speedometer signal like how the Dominator does for the transmission ICF and allow the use of the CAN Bus speedometer for those of us who don't want to use a Digital Dash with your ECU.

    I'm probably a small percentage, but heck if you don't ask the answer is going to be no anyway.

    Now I'm off to learn how to get an Arduino CAN Shield or SparkFun CAN shield or maybe something else to spit out OBDII PID-0D information to talk to the speedometer. Should be easy right? This is gibberish at the moment, I haven't got much time in to studying CAN Bus stuff yet. I'm full on Dunning-Kruger effect right now with not knowing what I don't know so I think I can probably hack this out quickly.

  4. #4
    Join Date
    Dec 2019
    Port Orchard, WA

    Post Learn a little more, understand a little less

    Since I am trying to communicate with the speedometer on the CAN bus I needed to know how the stereo jumper is wired. Holley does not provide the instructions for this. The instructions just say to direct wire to OBDII connector. Oddly enough the instructions don't mention anything about Holley ECUs, they only talk about OBDII.

    I asked Holley Tech: How do I direct wire the speedometer to the CAN bus for an ISO J1979 standard OBDII connector?

    The CAN bus is on pin 6 and 14 of the connector as mandated by the ISO J1979.

    It took three separate techs to get one to even respond to me. Not sure why my questions keep getting ignored.

    The third Tech's initial response was that “you can't, this speedometer only works with the Dominator ECU.”

    I have had more Techs than not say that the speedometer is OBDII CAN bus compatible as well as the Dominator and Terminator X Max with a gauge module. I pointed the tech to their own product documentation:

    Directly from Holley documentation (12/28/19). I bold and underlined the specifics I was referring to. I am not talking about all of the other incorrect information at this time, just the OBDII related stuff.
    Begin quote:

    Holley is pleased to announce the continuing evolution of its very successful analog-style gauges with the release of new 3-3/8" and 4-1/2" speedometers and tachometers to complement our 2-1/16" gauge line. These are designed specifically for use with Holley EFI systems or as a standalone unit and available in both black and white face versions. These gauges are compatible with all Terminator, HP, Dominator, and Sniper ECU's, allowing them to be installed in a variety of Holley EFI equipped vehicles.


    • Compatible with all Holley EFI touch screens, dashes, handheld tuners, and other CAN devices – Great for Holley EFI users looking to install a combination of needle gauges and LCD accessories
    • Slim-style mounting requires very little dash space for installation
    • 240° sweep pointer from 8 to 4 o’clock makes gauges easy to read at a glance
    • Internal microprocessor ensures accurate pointer movement in street and racing conditions
    • Spin lock ring threads to back of gauge case for simple and secure gauge mounting
    • CNC machined billet aluminum bezels with anodized finish – Bezels are threaded for easy replacement
    • Multiple bezel options available separately – User can customize the gauges to their preference
    • Wires directly into the vehicle's 16-pin OBDII data link connector
    • Operates by receiving data from the ECU (Engine Control Unit) through the OBDII data link connector
    • 0-160 MPH range with multi-function LCD display including mileage/trip odometer and peak speed recall

    End quote.

    Then I asked why they thought that it will not work on the OBDII CAN bus. They said they didn't know why the documentation as well as the instructions for installation talked about the OBDII. After repeated attempts of trying to get them to answer the question they sent a message to“Engineering.” I then had to wait for the Tech to get back to me.

    Holley Tech response:
    Begin quote:
    Here’s the info- The gauges are a custom look Speedhut gauge. I think the instructions were copy/pasted from the Speedhut book. They hook them up through OBD, we don’t.

    That being said,they should be the same wiring as the Speedhut Freedom gauges.
    End quote.

    That only helps me if I had a Speedhut stereo connector plug and cable,which Holley doesn't send with the gauge. I don't know if the Speedhut stereo connectors are wired with the red wire to the “tip”or “ring” and they don't provide specific enough documentation to figure it out.

    So I sent a question to Speedhut.
    Speedhut Tech support question:
    I have a GF4.5-SPEEDO-03 speedometer but not one of your stereo cables to connect to it.

    I have my own stereo cable that I can wire up but I don't know which wire to connect to the CAN High and CAN low wires because it doesn't have the same color wires as yours. Could you tell me which wires to connect to with the following list?

    1.Wire that connects to the "Tip" of the Stereo plug: CAN High \ CAN low \ ground \ none
    2.Wire that connects to the "Ring" of the Stereo plug: CAN High \ CAN low \ ground \ none
    3.Wire that connects to the "Sleeve" of the Stereo plug: CAN High \ CAN low \ ground \ none

    Speedhut Tech response: No response.

    I am realizing that “Tech support” is actually sales related and they don't actually know the engineering of the products. The only information I can ever get out of them is the same information that I can get from reading their own documentation, which has errors. I had to give up on Tech support. Unless I can talk directly to engineering I will not be able to get real answers.

    Here is what I found out on my own since no one is willing to help.
    The wiring of the Stereo connector for Speedhut/Holley CAN bus gauges:

    1. Wire that connects to the "Tip" of the Stereo plug: CAN High.
    2. Wire that connects to the "Ring" of the Stereo plug: CAN Low.
    3. Wire that connects to the "Sleeve" of the Stereo plug: none required, internally connected to power supply ground.

    When connecting to the CAN bus provided from the gauge module I found out that the gauge is communicating using the UDS CAN bus standard as expected since the gauge is OBDII compliant. What was unexpected was that the HP ECU\Gauge module is actually communicating with the Speedometer using the same standard.

    I had made an assumption that the HP ECU does not provide any communications for the speedometer. This is not true in a way. The gauge module communicates with the HP ECU and translates the information from the Holley ECU to the gauges. When I sent a request on the CAN bus to the ECU/Gauge module for what OBD standard it uses,the ECU/Gauge module responded - OBD-II as defined by the CARB.

    I requested for the Gauge module/HP ECU to respond with the supported Parameter IDs and it returned the code that it supports vehicle speed, among many others. This makes sense because Holley keeps saying that the Dominator ECU works, which means it would have to send the data with the correct Parameter ID through the Gauge module.

    If you connect the speedometer to the gauge module and power everything up while monitoring the CAN bus, the speedometer and the ECU/Gauge module start communicating. The gauge module is sending the correct response identification and the correct parameter identification for the speedometer. It is telling the speedometer that the speed is 0.

    Assuming that Holley didn't go to extra effort to make the Gage module provide a 0 speed signal to the gauge and since the Dominator ECU uses the same gauge module I made another assumption:

    This means that the HP ECU could be capable of taking the speed input from the custom input and sending it to the speedometer through the gauge module. Holley either has not needed to do this or are intentionally not doing it for some reason. I would have to talk to “Engineering”to find out why. I can see that since I am having so much trouble getting any knowledge out of Tech support for this gauge, there must not be that much demand to drive this “fix.”

    More to figure out. I don't know how to communicate with the HP ECU directly to be able to pick up the custom speed DATA that is being put on the CAN bus for use of the digital dashes, as long as you name the channel “speed.” If I can figure that out I will have this project beat. I can just translate the custom input speed data to the actual Speedometer data exactly the same way that the gauge module is doing for everything else.

    Then my whole goal of being able to use the Holley tuning software on my laptop to calibrate the speedometer through the custom input for changing tire sizes and swapping out 3rd members with different ratios while using their nice looking all matching gauges will be met. No GPS speedometer or unnecessary expensive, and in my opinion ugly, digital dash needed.

    I found that NHRA publishes PRO stock EFI Requirements for the HP EFI ECUs that they have mandated be used. It has a section titled “EFI CAN Bus Communications. This details how to get the information off of the HP and Dominator ECU. The documentation says "Holley Performance Products – For public release " and if you are interested in looking at it:

    On the website in the "Tech"section on the left - Select "NHRA Accepted Products." Then select "NHRA Accepted Product Specifications." Then select "Pro stock." Then select "NHRA Pro Stock Electronic Fuel Injection Requirements." "CAN Communications"starts on page 88 in this version.

    I found that the information allows you to at least communicate with the HP. Not all of the CAN IDs work as shown. I found that my Custom Input No. 4 is on CAN ID 0x1E051000 not on 0x1E055000 as the documentation says it would be. I also found that I could only read every other CAN ID shown in the table. I never did figure this out because I already know what I needed to know. I can extract my custom information from CAN ID 0x1E051000 and it calculates out to what the Holley EFI software is showing. My intention all along was to then change the CAN ID and send it to the Speedometer and dust my hands off. But...

    New problem: The Holley CAN bus runs at 1Mbit and the CAN bus gauge runs at 500Kbit. It is not possible to communicate on both buses at the same time with one CAN controller.

    The HP ECU is essentially running 2 CAN buses simultaneously, if you count the gauge module, and I would need to have two separate CAN bus controllers. One to talk to the ECU directly at 1Mbit/s and communicate with the other controller through one of its other com channels. Then the other CAN bus controller would talk to the speedometer at 500Kbit/s. I think I am going to draw the line here. It was fun so far but adding even more hardware into this mess is not worth it.

    I am going to take the Hall effect sensor signal directly off the transmission and process it in my CAN controller and then send the speed signal to the Speedometer separately from the Holley gauge module CAN bus. I have to keep the speedometer off the gauge module CAN bus because even though the HP ECU will not put a custom Speed input on the digital gauge bus for the speedometer, it is flooding the Speedometer with a zero speed signal for some unknown reason on both the gauge module bus and the ECU CAN bus. This prevents me from being able to send a speed signal while connected to any CAN bus.

    This is a pretty ridiculous solution, but my best choice with the current options I have available. The up side is I still get to custom calibrate the speedometer using my laptop. It just isn't as elegant as if Holley actually did what they advertised. Hopefully they will fix this problem in the future. I know it is fixable because the ECU is already processing and sending a speed signal, all they have to do is make it get the signal data from the available custom input and not a non existent one.

    Now you know how to succeed at making a Holley CAN bus speedometer work with the HP ECU, and how not to. I don't know what to recommend. Just determine how much you really want all of your gauges to match I guess and if you are willing to run a GPS speedometer, that is really at home on a boat, in your on land vehicle.
    Last edited by nicholaspurdy; 01-01-2020 at 07:07 PM. Reason: Added the final post, for some reason it got sent to another thread.

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