Rodeo 92 3.1L MAP Sensor

12-29-2010, 04:30 PM

I entered a hard terrain with my rodeo and on the first jump the truck dies, and it was hard to start it out again, I noticed that the check engine light came on, finally trying a lot the truck started but hard to keep it running with a lot of black smoke, I disconnected the MAP sensor (electrically) and the truck stabilize enough to keep it running, and get back home, I notice that it lost force when I tried to accelerate, then I connected the self diagnostic jumper and the truck is showing a 34 code which I believe is the MAP sensor, so I checked the ref voltage and is 5V but the signal from the sensor is 0V, so I checked the sensor disconnecting the harness but using a jumper set of cables to connect the ref 5V but the sensor wire from the harness, measuring the output of the sensor it reads fine the 4.5 volts and decreses when I apply vacuum as normal, but as soon as I connect the sensor wire from the harness in to the sensor the reading drops to 0V on the output of the sensor.

Any suggestion?? I checked the resistance between GND and sen wire and is about .2 Ohms not sure if that means that there is a short somewhere.

Please Help.

01-03-2011, 11:47 PM
As I explained earlier the MAP sensor works fine with the B wire umplugged and as soon as I connected the B wire to the MAP the sensor stops working, so I went ahead and check for any short from the sensor connector to the ECM connector and founs that it was OK, so I opened the ECU and found a Diode that was bad(short) so I replaced the diode and the problem went away for a couple of minutes, then it came back and it was intermitent, I accidentally moved the harness and found that the the MAP started works everytime I move the harness, so I check the entire harness and found that two of them where shorting out, the harness was close to a sharp edge close the battery so I insulate the cables to avoid the short, start the truck again and everything works fine now, so that explain why the truck started failing when I entered the hard terrain, the short may blow the diode in the ECM, and that's why the truck was failing, the code 34 says that is low voltage, so due to the short the ECM was reading 0V.

I hope this post helps someone else.

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