P0886 — TCM Power Relay Control Circuit Low

TCM power-relay control: The electrical input is below its permitted range. This signal-level finding does not by itself establish a mechanical failure. Relay control and feedback from the relay output are separate functions. The code does not establish whether the relay, wiring or controller is responsible.

Affected system: Transmission controller electrical supply

Symptoms

• Warning light may illuminate
• Related system function may be impaired
• Vehicle-specific symptoms vary

Possible causes

• Low or unstable supply voltage, fuse or relay fault, poor ground, or wiring damage
• Related wiring, connector, power or ground fault
• Vehicle-specific mechanical or control issue

What to check

• Record stored and pending codes and freeze-frame data
• Measure battery and charging voltage under load and compare with scan data; test the named circuit, fuse, relay, grounds and connectors.
• Confirm measured values against the vehicle service information
• Retest under the conditions that set the code
• Measure battery and charging voltage under load and compare with scan data; test the named circuit, fuse, relay, grounds and connectors.
• Repair the verified cause and confirm the code does not return

Also written as: P0886-00, P088600, PO886 (some scan tools add the fault-type byte, e.g. -00).