41TE NGC

P0891-TRANSMISSION RELAY ALWAYS ON







Theory of Operation

The Transmission Control Output circuit is used to supply power to the Transmission Solenoid/Pressure Switch Assembly and the PCM when in normal operating mode. The purpose of the Transmission Output circuit is to allow the Transmission Control System to turn off the power to the Transmission Solenoid/Pressure Switch Assembly in the event that the transmission should need to be placed into "limp-in" mode due to a DTC.

After a PCM reset, (ignition switch turned to the run position, or after cranking the engine) the Transmission Control System verifies that the Transmission Output circuit is open by checking for voltage on the Transmission Output circuits before the Transmission Control System request for the circuit to be powered up. The request is sent by a direct circuit control from the PCM to the TIPM. If voltage is detected on the Transmission Output circuits before the request is sent, the DTC will set.

- When Monitored:
When the ignition is turned from "OFF" position to "RUN" position and/or the ignition is turned from "START" position to "RUN" position.

- Set Condition:
This DTC is set if the Powertrain Control Module senses greater than 3.0 volts on the Transmission Control Relay Output circuits prior to a request from the PCM to TIPM to energize the Transmission Output circuits.





Always perform the 40/41TE Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure

1. CHECK FOR RELATED DTCS
1. With the scan tool check DTCs.

Are there any TCM Power Input DTCS present?

Yes

- Perform the appropriate diagnostic procedure.

No

- Go To 2

2. CHECK TO SEE IF DTC P0891 IS CURRENT
1. With the scan tool, check the Starts Since Set counter.

NOTE: This counter only applies to the last DTC set.

Is the Starts Since Set counter set to 0?

Yes

- Go To 3

No

- Go To 6

3. (T16) TRANSMISSION OUTPUT CIRCUIT SHORT TO VOLTAGE




1. Turn the ignition off to the lock position.
2. Disconnect the PCM C4 harness connector and connect Miller tool #8815.
3. Disconnect the TIPM C10 harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the PCM Pinout Box 8815 to perform diagnosis.

4. Ignition on, engine not running.
5. Measure the voltage of the (T16) Transmission Control Output circuits in the Miller tool #8815.

Is the voltage above 0.5 volts on any (T16) Transmission Control Output circuit?

Yes

- Go To 4

No

- Go To 5

4. CHECK THE TRANSMISSION SOLENOID/TRS ASSEMBLY




1. Turn the ignition off to the lock position.
2. Disconnect the Transmission Solenoid/Pressure Switch Assembly harness connector.
3. Ignition on, engine not running.
4. Measure the voltage of the (T16) Transmission Control Output circuits in the Miller tool #8815.

Is the voltage above 0.5 volts?

Yes

- Repair the (T16) Transmission Control Output circuit for a short to voltage.
- Perform 40/41TE TRANSMISSION VERIFICATION TEST 40/41TE Transmission Verification Test

No

- Replace the Transmission Solenoid/TRS Assembly.
- Perform 40/41TE TRANSMISSION VERIFICATION TEST 40/41TE Transmission Verification Test

5. CHECK THE (T15) TRANSMISSION CONTROL CIRCUIT FOR A SHORT TO VOLTAGE




1. Measure the voltage of the (T15) Transmission Control circuit.

Is the voltage above 0.5 volts?

Yes

- Repair the (T15) Transmission Control circuit for a short to voltage.
- Perform 40/41TE TRANSMISSION VERIFICATION TEST 40/41TE Transmission Verification Test

No

- Using the schematics as a guide, check the Powertrain Control Module (PCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the PCM. With the scan tool, perform Quick Learn Quick Learn Procedure.
- Perform 40/41TE TRANSMISSION VERIFICATION TEST 40/41TE Transmission Verification Test

6. CHECK WIRING AND CONNECTORS
1. The conditions necessary to set this DTC are not present at this time.
2. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
3. Wiggle the wires while checking for shorted and open circuits.
4. With the scan tool, check the Event Data to help identify the conditions in which the DTC was set.

Where there any problems found?

Yes

- Repair as necessary.
- Perform 40/41TE TRANSMISSION VERIFICATION TEST 40/41TE Transmission Verification Test

No

- Test Complete.