P0891: Transmission Control Module Power Relay Sense Circuit High
What to do
If the transmission still shifts normally, the power is reaching the module and only the monitoring circuit is faulty — a smaller job. If it is stuck in one gear, the relay itself is more likely.
What this code means
The relay sense circuit reads above its valid range — an open circuit or a short to supply — which the module takes as the relay never closing. If that reading is accurate the module has no main supply and the transmission is running without electronic control; if it is a sense circuit fault, everything is working and the module simply cannot see it.
How the vehicle drives distinguishes the two immediately. A transmission shifting normally with this code stored is telling you the relay is fine and the sense circuit is the fault.
Likely causes
Start here
- Open circuit in relay sense wiring · moderate
- Corroded or loose connector · easy
- Faulty transmission control module power relay · easy
Less common
- Blown fuse or failed supply · easy
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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