4L80E Automatic Transmission

DTC 81:

Ratio Circuit:

CIRCUIT DESCRIPTION
The PCM/TCM continually monitors voltage on each circuit connected to the quad driver looking for either low or high voltage depending on the commanded state of the devices connected. Code 81 will set if a fault has been detected on the 2-3 shift solenoid circuit. If 2-3 shift solenoid is commanded "ON" by the PCM/TCM, the voltage should drop when the solenoid is grounded, if the voltage stays up for at least 2 second, Code 81 will be set. The opposite is also true if 2-3 shift solenoid is "OFF" then the voltage on the circuit should remain high, if voltage drops for more than 2 second, then Code 81 will be set.

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. This procedure checks the 2-3 shift solenoid and the internal transmission wiring for shorts.

2. This tests checks for power to the 2-3 shift shift solenoid from the ignition through the transmission fuse.

3. This test verifies that CKT 1223 is not shorted to ground.

4. This test checks the ability of the PCM/TCM to ground or control the 2-3 shift shift solenoid.

5. This test verifies that CKT 1223 is not shorted to ground.


DIAGNOSTIC AIDS
Check all connections, especially those at the transmission pass-thru connector.
Refer to Diagnosis By Symptom Testing and Inspection