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Diagnostic Procedure

WARNING: This page is about a different car, the 2005 Jeep Liberty. However, it is still accessible from the selected car via links, so may be relevant.
DIAGNOSTIC TEST REFERENCE - P0888-RELAY OUTPUT ALWAYS OFF

TEST ACTION APPLICABILITY
1
NOTE: Low fluid level can be the cause of many transmission problems. If the fluid level is low locate and repair the leak then check and adjust the fluid level per the Service Information.
NOTE: Always perform diagnostics with a fully charged battery to avoid false symptoms.
With the DRBIII®, read the engine DTC's. Check and repair all engine DTC's prior to performing transmission symptom diagnostics.With the DRBIII®, read Transmission DTC's. Record all DTC's and 1 Trip Failures.
NOTE: Diagnose 1 Trip Failures as a fully matured DTC.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.Repair as necessary.Perform the Shift Lever Position Test. If the test does not pass, refer to Symptom test for P0706 CHECK SHIFTER SIGNAL .For Gear Ratio DTC's, check and record all CVI's.Most DTC's set on start up but some must be set by driving the vehicle such that all diagnostic monitors have run.
NOTE: Verify the flash level of the transmission controller. Some problems are corrected by software upgrades to the transmission controller.
NOTE: Check for applicable TSB's related to the problem.
Perform this procedure prior to Symptom diagnosis.ContinueGo To 2		 All
2 With the DRBIII®, Check the STARTS SINCE SET counter for P0888.
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 11		 All
3 Turn the ignition off to the lock position.
Remove the Transmission Control Relay from the PDC.
NOTE: Check connectors - Clean/repair as necessary.

Using a 12-volt test light connected to ground, check the Fused B(+) circuit in the Transmission Control Relay connector.
NOTE: The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Does the test light illuminate brightly?
Yes --> Go To 4
No --> Repair the Fused B(+) circuit for an open. If the fuse is open make sure to check for a short to ground.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .		 All
4 Turn the ignition off to the lock position.
Disconnect the Transmission Control Relay from the PDC.
NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between ground and the Transmission Control Relay ground circuit in the Transmission Control Relay connector.
Is the resistance above 5.0 ohms?
Yes --> Repair the Transmission Control Relay Ground circuit for an open.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No --> Go To 5		 All
5 Turn the ignition off to the lock position.
Disconnect the TCM harness connector.
Disconnect the Transmission Solenoid/TRS Assembly harness connector.
Remove the Transmission Control Relay from the PDC.
NOTE: Check connectors - Clean/repair as necessary.

Connect a jumper wire between the Fused B(+) circuit and the Transmission Control Relay Output circuit in the Transmission Control Relay connector.
Using a 12-volt test light connected to ground, check the all three Transmission Control Relay Output circuits in the TCM harness connector.
NOTE: The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Does the test light illuminate brightly on all three circuits?
Yes --> Go To 6
No --> Repair the Transmission Control Relay Output circuit for an open or high resistance.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .		 All
6 Turn the ignition off to the lock position.
Disconnect the TCM harness connector.
Remove the Transmission Control Relay from the PDC.
NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between ground and the Transmission Control Relay Output circuit.
Is the resistance below 5.0 ohms?
Yes --> Repair the Transmission Control Relay Output circuit for a short to ground.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No --> Go To 7		 All
7 Turn the ignition off to the lock position.
Disconnect the TCM harness connector.
Remove the Transmission Control Relay from the PDC.
NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance of the Transmission Control Relay Control circuit between the Transmission Control Relay connector and the TCM harness connector.
Is the resistance above 5.0 ohms?
Yes --> Repair the Transmission Control Relay Control circuit for an open.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No --> Go To 8		 All
8 Turn the ignition off to the lock position.
Disconnect the TCM harness connector.
Remove the Transmission Control Relay from the PDC.
NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between ground and the Transmission Control Relay Control circuit.
Is the resistance below 5.0 ohms?
Yes --> Repair the Transmission Control Relay Control circuit for a short to ground.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No --> Go To 9		 All
9 Turn the ignition off to the lock position.
Disconnect the TCM harness connector.
Remove the Transmission Control Relay
NOTE: Check connectors - Clean/repair as necessary.

Connect a jumper wire between the Fused B(+) circuit and the Transmission Control Relay Output circuit in the Transmission Control Relay connector.
Measure the voltage of the Transmission Control Relay Output circuit in the TCM harness connector.
Is the voltage above 10.0 volts?
Yes --> Replace the Transmission Control Relay.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No --> Go To 10		 All
10 Using the schematics as a guide, inspect the wiring and connectors. Repair as necessary. Pay particular attention to all power and ground circuits.
If there are no possible causes remaining, view repair.
Repair
Replace the Transmission Control Module per the Service Information. WITH THE DRBIII® PERFORM QUICK LEARN 
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .		 All
11 The conditions necessary to set this DTC are not present at this time.
Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
Wiggle the wires while checking for shorts and open circuits.
With the DRBIII®, check the EATX DTC EVENT DATA to help identify the conditions in which the DTC was set.
Were there any problems found?
Yes --> Repair as necessary.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1 .
No --> Test Complete.		 All
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