P0891 Fault Code

TCM Power Relay Sense Circuit High

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0891 code indicates an issue with the Transmission Control Module (TCM) power relay sense circuit, specifically that the circuit is reading a higher voltage than expected. This can affect the functionality of the TCM, leading to improper shifting or other transmission issues.

• The TCM controls various operations of the transmission, and the relay is crucial for providing power to the module.
• Identifying this issue often requires a thorough understanding of the electrical systems in the vehicle, as well as familiarity with OBD-II diagnostic tools.

What are the symptoms of the P0891 code?

Symptoms associated with the P0891 code may include:

• Transmission not shifting properly, either harshly or slipping.
• The vehicle may enter 'limp mode', restricting performance while protecting the transmission.
• Warning lights may appear on the dashboard, such as the check engine light.
• Difficulty in engaging or disengaging gears.

What causes the P0891 code?

Common causes for the P0891 code include:

• Faulty TCM power relay or relay circuit.
• Wiring issues, such as short circuits or corrosion in the connections.
• Defective Transmission Control Module (TCM).
• Problems with the vehicle's main power distribution that affect the relay circuit.
• Poor ground connections for the TCM or relay.

How to fix P0891?

To resolve the P0891 code, consider the following steps:

• Inspect the TCM power relay and replace it if faulty.
• Check wiring and connectors for damages, corrosion, or loose connections and repair as needed.
• Test the TCM for any internal faults and replace it if necessary.
• Ensure proper grounding for the TCM and related circuits.
• Clear the code and perform a test drive to see if the issue has been resolved.