Fix P0891: STEP-BY-STEP diagnostic GUIDE!

The P0891: TCM Power Relay Sense Circuit High refers to a condition where the transmission control module (TCM) power relay sense circuit is detecting higher than expected voltage. This can interfere with the TCM’s ability to manage the transmission, leading to performance issues.

P0891 – Quick Overview

CodeInformation
MeaningP0891: TCM Power Relay Sense Circuit High
Is it serious?Yes, this can lead to transmission performance problems or damage to the TCM.
Possible causes– High voltage in the TCM power relay sense circuit
– Faulty TCM power relay
– Wiring or connector issues
How to diagnose?– Test the circuit for high voltage
– Inspect wiring and connectors
– Replace faulty components if needed

P0891 Meaning

The P0891 code indicates that the TCM is detecting a higher than normal voltage in the power relay sense circuit. This could result from a faulty power relay, damaged wiring, or poor connections. Excessive voltage may prevent the TCM from regulating transmission functions properly, causing shifting issues or transmission failure.

Step-by-step diagnostic guide

ActionDescriptionTools Needed
Check for Other CodesUse an OBD-II scanner to check for additional related codes.OBD-II Scanner
Inspect Wiring and ConnectorsInspect the wiring and connectors related to the TCM power relay for damage, corrosion, or loose connections.Flashlight, Multimeter
Test TCM Power Relay Sense Circuit for High VoltageUse a multimeter to test the circuit for high voltage. Compare the reading to manufacturer specifications.Multimeter, Vehicle Manual
Test the TCM Power RelayTest the power relay to ensure it is functioning properly. Replace if necessary.Multimeter, Replacement Relay
Replace Faulty ComponentsReplace any faulty wiring, connectors, or the TCM relay if needed.Replacement parts, Tools
Clear Code and Test DriveAfter repairs, clear the code and perform a test drive to ensure the problem is resolved.OBD-II Scanner, Vehicle Owner’s Manual
Recheck for CodesRe-scan the vehicle after the test drive to confirm that the P0891 code does not return.OBD-II Scanner
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