P2771
DTC P2771
Circuit Description
The four-wheel drive (4WD) low signal circuit is used to notify the transmission control module (TCM) that the vehicle is in 4WD low range.
DTC P2771 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P2771 4WD Low Switch Circuit
Conditions for Running the DTC
* DTCs P0721 and P0722 are not active.
* 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.
* Output speed is greater than 60 RPM.
* Transmission fluid temperature (TFT) is between 20-130°C (68-266°F).
* The shift is complete and NEUTRAL range is not selected.
Conditions for Setting the DTC
DTC P2771 sets when one of the following conditions occur:
* The transfer case switch indicates high range, and the calculated range is low range for 5 seconds or greater.
* The transfer case switch indicates low range, and the calculated range is high range for 5 seconds or greater.
Action Taken When the DTC Sets
* The TCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
* DTC 2771 is stored in TCM history.
* The TCM inhibits torque converter clutch (TCC) engagement.
Conditions for Clearing the MIL/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.
* Inspect for any transmission DTCs that may have set again.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. This step tests the status of the 4WD low switch.
3. This step tests for a 4WD switch failure to ground.
4. This step tests for a short in the wiring harness.
9. This step tests for a 4WD switch failure to an open state.
10. This step tests for an open in the wiring harness.
Step 1 - Step 8:
Step 9 - Step 16:
