reverse only with 0700 code

[92 TY 1173]

Yeah, I talked to the local Allison dealer. They said with that code and still having reverse in limp it is most likely a wiring issue. Prolly a break between the trans and the tcm. I'm thinking it was when I moved the tcm to get to the ecm. Yeah, likr trying to find a needle in a haystack.

[suttert]

Doesn't sound like fun, bring beer!

Sent from my ADR6325 using AutoGuide.Com Free App

[white drtymax]

make sure all your grounds are clean and tight and make sure the TCM is getting the right voltage and not shorting out when you put the truck in reverse.

[jc1843]

Most likely you have a loose connector in the TCM. Remove the connectore and inspect the terminals, bet one is not seated correctly.

[white drtymax]

or a typical problem on the lb7 is the steering pump pulley rubbing through the wiring harness going to the TCM, so check the wiring harness all the way through and replace any bad wires.

[houstonlb7]

2002 GMC Truck GMC K Sierra - 4WD | Sierra, Silverado VIN C/K Service Manual | Document ID: 1477677
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DTC P0876


Circuit Description


The pressure switch manifold (PSM) is a multiple-switch assembly made up of three normally open (N/O) pressure switches and one normally closed (N/C) pressure switch for reverse pressure. Fluid pressure is supplied to the reverse pressure switch when the manual selector valve is in any position, except REVERSE. When the manual selector valve is moved to REVERSE, pressure to the reverse pressure switch is cut off causing the switch to close.

DTC P0876 is a type B DTC.

Conditions for Running the DTC
• The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts.
• Engine speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds.
• Transmission fluid temperature (TFT) is greater than 0°C (32°F).
• DTCs P0708 and P0875 are not active.


Conditions for Setting the DTC

DTC P0876 sets when a forward range has been selected and the reverse pressure switch remains in the mechanically open/electrically off position for more than 1 second.


Action Taken When the DTC Sets
• The transmission control module (TCM) illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
• The transmission will lock in NEUTRAL.
• DTC P0876 will be stored in TCM history.
• The TCM freezes shift adapts (DNA).
• The TCM inhibits torque converter clutch (TCC) engagement.


Conditions for Clearing the DTC

A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.


Diagnostic Aids
• Inspect the wiring for poor electrical connections at the TCM. Inspect for the following conditions:
- A bent terminal
- A backed-out terminal
- A damaged terminal
- Poor terminal tension
- A chafed wire
- A broken wire inside the insulation


• When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
• You may have to drive the vehicle in order to experience a condition.
• This DTC could indicate a hydraulic leak path exhausting pressure from the reverse pressure switch.



© 2013 General Motors. All rights reserved.

[houstonlb7]

Looks like if you did bump a wire it'll be a LT GRN/BLK wire in pin 4

[92 TY 1173]

Houston lb7, awesome post that did the trick. I unplugged the TCM and found the number four pin cleaned it up rechecked the wiring and put it back together and it works like a charm. I appreciate the help. Fantastic!!

[houstonlb7]

Glad I could help bro, good to hear.