I recently purchased a 2015 Fusion that had a P0141 O2 sensor error, car ran fine. Then, my daughter was driving it and it went into limp mode. Hooking it up to my code reader, this is what I saw :
Cleared the codes and got it home. Then ran fine.
CAR BACKGROUND
According to the carfax, the car has been wrecked on both the left and right front, on different occasions.
WHAT I’VE DONE SO FAR
Took it to my mechanic. He started it up in the morning, went into LIMP mode again. He cleared codes, drove it 50 miles with no issue.
Got it back, went into limp mode again. For the most part, same errors, with a new P06A7 “Computer and Auxiliary Outputs” error.
Looking at sensor readings while running in limp, noticed MAP sensor was reading 0 PSI. Unhook sensor and reading goes high. Decided to replace MAP. Ran fine, then limp. Thinking it was a bad ground, potentially due to the wrecks, I ran a wire between passenger side and battery. Restarted car and ran fine. Noticed MAP was responding with throttle, etc anywhere from 10PSI to 25PSI. Let it sit for a few minutes restarted, limp again. MAP was back to 0 PSI.
Not sure where to go next. The MAP acting weird makes me think there is a larger, potentially electrical problem.
Thoughts please?
My dimwit diy’er w/no fusion experience thinking is that it is a good idea to focus on the MAP problem first. My Corolla though does use a MAP sensor, so some experience w/ that. With the engine not running, what does the MAP sensor read according toyour scan tool? It might read 15 psi (atmospheric pressure) or 0 psi, meaning the atmospheric pressure has been subtracted out.
Something seems amiss, maybe. If the map sensor reads 0 psi with engine off, it should read about -10 psi at idle. -10 psi is roughly -20 inch hg, common reading for intake manifold at idle w/good compression engne. So that all s ok, you just assume the minus sign. The reading when not at idle are probably caused by the turbo boost, so hard to say if that’s ok. But it appears the map sensor is reasonably accurate.
Sure smells that way. I did see a repair to part of the harness by the battery/drivers side. 3 wires. Ohmed it out and was good. Not sure if I just go to splicing or what.
I may be wrong . . . and I’m thinking of various L1 composite vehicles . . . but I believe as far as the voltages go, one starts low and goes high, whereas the other starts high and goes low
Agreed. Although sensors C and D produce opposite voltage signals as the throttle position changes, they should sum to 5.0V at all times if they’re operating properly. However, their respective % positions should be the same IMO. I believe that limp mode in this vehicle is caused by one TPS sensor fault combined with a MAP fault or both TP sensor faults. Are you getting a TPS code? Your screenshot says there are 10 codes but the photo only shows 8 of them.
How confident are you that the battery is good? You mentioned you ran a ground wire from the battery to the body but have you checked the engine to body ground? Check the voltage drop between a good chassis ground and the engine. Should be less than 0.1 volts with the engine off. If your voltmeter has a min/max mode, you can use that to measure the drop while the engine is running to see if you have a higher intermittent voltage drop. Low battery voltage can cause multiple circuits to register codes and put it in limp mode on vehicles with electronic throttle control.
On the battery, I left it on charge overnight. First start is in limp mode. Bat voltage is 12.92. Neg terminal to body is 0.02 ohms, 0V difference. Battery code looks like a 2020 though.
Something to consider. Camshaft sensors and MAP both threw errors AND share blue/white from this Mitchell schematic, which goes to VREF. Any thoughts there?
