Engine-Codes - Generic - P0891

P0891 - TCM Power Relay Sense Circuit High

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3  What is this?

P0891 Possible Causes

  • Faulty Transmission Control Module (TCM) Power Relay
  • Transmission Control Module (TCM) Power Relay harness is open or shorted
  • Transmission Control Module (TCM) Power Relay circuit poor electrical connection

How do I fix code P0891

Check the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.

Cost of diagnosing the P0891 code

Labor: 1.0

The cost of diagnosing the P0891 code is 1.0 hour of labor. The auto repair labor rates vary widely across the country, and even within the same city. Most auto repairs shops charge between $75 and $150 per hour.

Possible Symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)

P0891 Meaning

The transmission control relay is used to supply power to the solenoid pack when the transmission is in normal operating mode. When the relay is off, no power is supplied to the solenoid pack and the transmission is in Limp-in mode. The relay output is fed back to the Powertrain Control Module (PCM). It is referred to as the Transmission Control Relay Output circuit or switched battery.
Immediately after a controller reset (ignition key turned to the run position or after cranking engine), the PCM verifies that the relay contacts are open by checking for no voltage at the switched battery terminals. After this is verified, the voltage at the pressure switches is checked. There should be no voltage on the pressure switches at this time. The PCM will then activate the relay.

P0891 More Information

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