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Thread: Odd sensor readings (TPS, MAP, fuel pressure, oil pressure) trying to find cause!

  1. #1

    Default Odd sensor readings (TPS, MAP, fuel pressure, oil pressure) trying to find cause!

    I'm having wierd issues with these sensors hovering around different values and bouncing around slightly. This happens whether the engine is running or not. Randomly my sensors will hover at a different value than they actually are (TPS hanging around 3-4% when it's actually 0, MAP sensor with engine of at that time will hover at say 108 kPa instead of 98-99, oil pressure will be 2-3 psi instead of 0, same with the fuel pressure. I wouldnt have even noticed this before because they're pretty close to the right values, but last time I rode they were bouncing around a little more than normal, which made my fueling enriched as the ECU tried to feed the motor based on the elevated kpa and than as these sensors spiked around I started getting Acceleration Enrichment when I wasnt doing anything. Oddly its all the sensors moving around together at the same time. Anyone have any idea what this sounds like and where to start with the troubleshooting?

  2. #2
    Join Date
    Dec 2009


    See note #4: (System Relay & Injector Wiring Troubleshooting)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Holley Dominator MPFI & DIS, 36-1 crank trigger, 1x cam sync, 200A 3G alternator, Optima Red battery, R134a A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM converter, B&M Hammer shifter, Stifflers trans crossmember & driveshaft safety loop, 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 M/T Street Comp tires.

  3. #3


    I'd troubleshoot your 5V reference network. All the 5V sensors run off pins A26 & A18, which are 5V reference & sensor ground, orange & black/white wires respectively. I'd start by unplugging one sensor at a time to see if maybe you have one bad sensor that's throwing the others off. Andrew

  4. #4


    Yeah, I've run into that exact thing before where one sensor has a high resistance leak to ground and the voltage loss is enough to drag all of the other sensors off target. I've also seen situations where the 5V regulator gets messed up and all the gauges read wrong. One bad sensor messing up all of the other sensors is the most likely culprit.

  5. #5


    Thank you guys! In my case it was an interminnent bad TPS sensor. Thank you to everyone for chiming in!

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