With a new battery reading 12.5V with key on I still have Engine Performance Reduced on the dash and it will start and turn over a few times on its own. Because of the OBDII scanner showing the MAP reading so low (1.9 psi compared to the Barometric reading at 12.5 psi), I suspect this is at least part of my issue. I have plugged the scanner into a couple of other vehicles and all of them the MAP and Barrometric readings match each other. If I remember right they were all about 12.5 psi for both MAP and Baro.

I decided to back probe the sensor connection. The blue wire is only reading 40mV and based on the wiring diagram it looks like that should be the 5v supply. The blue/green wire is reading 0.48V. I replaced the MAP sensor and the MAP reading is still 1.9 psi.


screen shot of Electronic Engine Controls sheet 2

I wiggled wires while I had my daughter watch the OBDII MAP reading to see if it changed but so far nothing changed it. I plan to check continuity from the ECM connection for the blue wire to the sensor connector. Any other suggestions of tests? Am I jumping the gun again like I did before replacing the battery?

EDIT: I did just read another thread where one step around the electrical issues is to perform a hard reset, disconnect both battery cables, touch them together for 10 seconds and wait 10 minutes. I will try that first.

 

What are your current OBD2 codes since you last cleared them? P0069 indicates a deviation between the MAP and Baro.

 

There aren't any active codes but the pending codes are P0069, P2138, and P0642.

The P0642 seems like it could be because the voltage at the MAP sensor isn't 5 volts.

 

Agreed. The low voltage issue (P0642) caused by a wiring/connector fault may be the cause of the two sensor codes. Wiring issues are tough to diagnose, especially when you have so many wires in a harness.

One of my frustrations with the wiring diagrams is that they don't provide more info. In addition to the wire color, I would like to see the voltage level. And where the signal is PWM, I would like to see the peak voltage and frequency.