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I have not figured out the map sensor code. I ran a jumper because I thought it was shorted but I think I was wrong about that. running a jumper didn't change anything and when I unplugged the harness from the ecm it was reading in the k ohms range. I'm reading 2.2V with the engine running at about 8-900rpm so I think the sensor is working. If the circuit and sensor is fine then what else would cause a map sensor code?
I've had it running for about an hour now trying different things so I'll have to get the key on cold reading later. I ran another jumper from the map plug to negative terminal of battery to eliminate that as an issue. I put a tube on the sensor so I can back probe it easier and monitor the 5v which it's staying constant 5v. Something strange I noticed is that when the reference wire is not connected to the ecm, it will read around 2.2v at idle but when I connect it it will drop to 0.
Do you have the "W" or "Z" engine code (8th vin position)?
Do you have a scanner that can report the pressure value being reported by the ECM or are we only working with the voltage output from the MAP sensor itself? If its the later then don't worry about the engine being cold.
We need some definitions on the three MAP wires. There are two reference wires: 5V ref (+5v power) and lo ref/sensor ground/5V return (different names for the same low noise sensor ground). Then there is the third wire, the sensor output.
Try applying 5v rev and lo ref to the sensor from the harness/connector and reading the output signal directly from the sensor with no connection to the harness. What do you get at idle and key on engine off?
So with the "W" code the terminology used is 5 volt ref and 5v return for the two power wires. That engine off value looks good and the idle value is in the ballpark. There are so many ranges quoted for idle on an analog map sensor. Ive seen 0.5-1.5, 1.5-2.5, and 1-2v. I'm not sure if that's a good idle value but it is working. P0107 code is for a reported map value below 0.5 volts so the possibilities are:
A wiring or connector problem
The MAP sensor cannot drive the load of the wire and ECM input
The ECM is bad
Now that we have terminology for the two reference wires tell me again what your experiments showed? And tell me again about the jumper wire. Use sensor output, 5v ref and 5v return to describe the wires since that what's on your wiring diagrams.
Ok so first problem I see is that the sensor output wire, when disconnected from the ECM and disconnect from the MAP sensor, is reading 16 ohms to the negative terminal of the battery. If I'm not mistaken, this is a dead short to ground that should not be there. This is where my jumper wire comes in. I ran a wire from the sensor output of connector of the MAP sensor to the back of the ECM.
For the jumper wire to tell you anything you have to have the sensor output wire disconnected at both the Map sensor and at the ECM. That would require you to cut the wire at the ecm and either also cut it at the sensor or power the sensor with jumpers with the sensor unplugged from the harness. Then run the jumper wire from the isolated sensor output to the pigtail wire into the ECM that resulted from cutting the lead. the original map sensor output wire is not touching anything at either end.
Make sure to cut wires with enough meat left to solder them back together
Correct. That's what I've done. Original sensor output wire is cut at the MAP sensor connector and cut at the ECM connector. I verified its the correct wire by color and also with the multimeter. It shows a dead short across each cut end and then it also shows a shows a dead short across either cut end to the negative terminal of the battery.
08-06-2021, 05:51 PM
