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
Code | Information |
---|---|
Meaning | P0891: 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
Action | Description | Tools Needed |
---|---|---|
Check for Other Codes | Use an OBD-II scanner to check for additional related codes. | OBD-II Scanner |
Inspect Wiring and Connectors | Inspect 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 Voltage | Use a multimeter to test the circuit for high voltage. Compare the reading to manufacturer specifications. | Multimeter, Vehicle Manual |
Test the TCM Power Relay | Test the power relay to ensure it is functioning properly. Replace if necessary. | Multimeter, Replacement Relay |
Replace Faulty Components | Replace any faulty wiring, connectors, or the TCM relay if needed. | Replacement parts, Tools |
Clear Code and Test Drive | After repairs, clear the code and perform a test drive to ensure the problem is resolved. | OBD-II Scanner, Vehicle Owner’s Manual |
Recheck for Codes | Re-scan the vehicle after the test drive to confirm that the P0891 code does not return. | OBD-II Scanner |

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Hi, I am Juraj “Yuri” Lukacko. I got frustrated by unhelpful and scammy mechanics, so I decided to learn everything about car diagnostics myself. I test dozens of new car diagnostic tools every month along with learning new strategies to fix and customize cars. About Juraj Lukacko (Yuri)