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MAP output failing

Sippola

New Member
Mar 8, 2023
4
4
Truck Year
2016
Hi all, 2016 stock truck with 184k KM. Last couple weeks I’m getting a P0108 code and a “Service electronic throttle“ message. Clear the code, then on first start, Code reader shows the MAP output at 85 engine off (which is good). Gives reasonable results for the first couple miles, then the graph starts showing spikes more and more often, up to 255 (not good), where after a few more miles, it stays high. Next morning, same deal. The colder the morning, the longer it runs fine. Seems like a bad wire, connection, or sensor. First tried cleaning, then Replacing the MAP sensor, no change. I’ve tried wiggling all the connections and wires and fuses and relays I can find when it’s reading high - no change. I’ll try again in the morning when it should be reading low again, maybe a fault from working to not working will be easier to find than the other way around.

P0108- high manifold absolute pressure make’s sense as the bad output is high. Which triggers the throttle message, also makes sense. I think the MAP info just isn’t getting to the ECU.

Engine below freezing makes it work for a bit. Bumps and brakes make the MAP output graph start to spike and continue spiking down from 255 for a while, then steady at 255.

It’s quite drivable, but certainly lower power.

Any trouble shooting ideas?
 

Multiplex49

New Member
Aug 19, 2022
8
1
Truck Year
2017
Clean the MAP sensor. Use a can of MAF sensor cleaner.
Don’t unplug the sensor.
Just one screw holds it in place.
Clean it.
Clear all codes.
 

Sippola

New Member
Mar 8, 2023
4
4
Truck Year
2016
Cleaned it, no change so then i replaced it.

i did find out yesterday the problem is at the 20 pin connector mounted on the passenger side of the engine. Wiggling that would show a spike on the code reader graph. Haven’t found which exact wire is the problem, and the MAP sensor wires are not the same colour at this connector. I’ve found two of the three, but the 3rd wire doesn’t seem to go there.
 

Sippola

New Member
Mar 8, 2023
4
4
Truck Year
2016
Found the problem, it’s the wire from the MAP or Boost sensor pin 4 to the PCM Pin 40. The connector that would show spikes in the data when when wiggled has no direct link, but it joins the main engine wiring harness about mid way, and I suspect that’s where the problem will be. I’ll have to open up the harness there, look for damage. If i can’t find the problem, I’ll put a pin in the wire and check for resistance each way. Then splice in a replacement. Not doing it just now, as it all works except the turbo output is either off or low output.
 
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