P0113 IAT Error when LMM in Reverse

Rickyb013

New member
Jun 21, 2020
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I have an 2007.5 2500 with LMM. I'm running a CTS Edge Tuner and started monitoring the IAT as I was continuously getting P0113 Codes that could readily be Cleared with the Tuner. I started noticing that the IAT would intermittently read -40 Degs when I was backing the Truck up. It never faults in Drive. When in Reverse, if the IAT flashes -40 Degs for more than a second or 2, the P0113 Code pops ... and then I have to clear it again.

Anybody seen this before. Seems like it could be electrical, but I can't understand what could be an Shared Electrical between the Tranny and the IAT..... why when in Reverse only, the IAT gets a bad read ??
 

Ron Nielson

Member
Oct 11, 2009
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Berryton, KS
See attached. Clearly you have a circuit problem. Exactly why the interface with being in reverse cannot be understood until you find the circuit problem.
 

Attachments

Rickyb013

New member
Jun 21, 2020
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Thanks Ron. I looked at the Diagnostics on the attachment and doesn't really help me. I could perform all those Diagnostics and the ECM and the Sensor would both show a pass. In any condition other than the truck being in Reverse, the Output of the Sensor would be at a voltage that indicates within an expected range. I actually replaced the IAT Sensor about 6 months ago believing it was faulty. It was only after I installed the Tuner that I could watch the IAT drop to -40 (4.8 Volts) when in Reverse.

I was hoping somebody out there might have seen this same phenomena and could share what fixed it. To be honest, I'm not even sure where to start looking for a change in Voltage from the IAT just because the Tranny is in reverse ?
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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Phoenix Az
start looking for broken wires or a cut area around the engine. if the motor mounts are going, you may have a damaged wire/s somewhere that when put in reverse, the looser motor mounts are causing them to pull apart. you may have to have someone hold the brake and keep it in reverse, then do the test procedures.
 

KyleC4

Tech
Dec 30, 2016
376
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Bay Area
jack up the rear of the truck and set axle on jack stands to keep wheels off ground. Then put vehicle in reverse and start your testing. Might need to have one of those brake pedal depresser or if you got a good holding parking brake. James is probably right is my guess. As the motor shifts load sides during reverse engagement it stresses the harness/wiring in different way.
 

Ron Nielson

Member
Oct 11, 2009
312
18
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Berryton, KS
The MAF and IAT sesnor is a 2 in one device. Both sensors feed a signal to the ECM, and the MAF signal goes to pin 5 on connector X-1 (the black connector) and the IAT signal goes to pin #42 on the same connector. It is a tan wire.

Somewhere between the sensor itself and the ECM the signal wire is being corrupted with either an open circuit (broken wire) or short to voltage. On the connector to the MAF/IAT, the yellow wire on one side of the connector is the MAF signal wire, the tan wire on the other end is the IAT signal wire. So follow the tan wire in the loom from the sensor to the ECM to discover the problem area. It will likely be much harder to find the exact problem spot than to do the repair. Also, you could jumper a separate from the IAT sensor signal at the MAF/IAT connector direct to the ECM to test the situation.
 

Rickyb013

New member
Jun 21, 2020
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Hey ... should have updated this Thread a Long time ago, but thought I will now to help somebody else someday. Issue is Resolved As per the feedback from Ron Nielson and Chevy 1925, I found a "Pinched" wire harness going into the MAF/IAF Sensor that was intermittently loosing continuity. I replaced the harness ... Issue Gone. Thanks for the help guys
 
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