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Engine-Codes – Generic – P0891

P0891 Code - TCM Power Relay Sense Circuit High

Quick Answer

The P0891 diagnostic trouble code (DTC) indicates a problem with the Transmission Control Module (TCM) power relay sense circuit being high. Common causes include Faulty TCM power relay, Damaged wiring harness or connector in the power relay sense circuit, Malfunctioning TCM. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P0891 indicates TCM Power Relay Sense Circuit High.
Common causes
Common causes include Faulty TCM power relay, Damaged wiring harness or connector in the power relay sense circuit, Malfunctioning TCM.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Sep 09, 2024
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Code P0891 Description

The P0891 diagnostic trouble code (DTC) indicates a problem with the Transmission Control Module (TCM) power relay sense circuit being high. The TCM is a crucial component of the vehicle's transmission system, responsible for controlling the shifting of gears and ensuring smooth operation. The power relay sense circuit is designed to monitor the voltage levels in the TCM power relay, which supplies power to the TCM. When the voltage in this circuit is detected to be higher than the specified threshold, the P0891 code is triggered.

OBDII Code P0891 - TCM Power Relay Sense Circuit High
P0891 Code - TCM Power Relay Sense Circuit High

Common Causes of P0891

  1. Faulty TCM power relay
  2. Damaged wiring harness or connector in the power relay sense circuit
  3. Malfunctioning TCM
  4. Electrical issues in the vehicle's system
  5. Corrosion or poor connections in the circuit

Symptoms of P0891

  1. Erratic shifting behavior
  2. Transmission slipping or hesitation
  3. Illuminated check engine light
  4. Reduced fuel efficiency
  5. Loss of power or acceleration

How to Fix P0891

  1. Begin by performing a thorough diagnosis of the TCM power relay sense circuit to pinpoint the exact cause of the high voltage issue.
  2. Inspect the TCM power relay and test it for proper functionality. Replace the relay if it is found to be faulty.
  3. Check the wiring harness and connectors in the power relay sense circuit for any damage or corrosion. Repair or replace as needed.
  4. Test the TCM for proper operation and reprogram if necessary. Replace the TCM if it is determined to be malfunctioning.
  5. Clear the trouble codes from the vehicle's system and test drive to ensure that the issue has been fully resolved.

Cost to Fix P0891

The typical repair costs for addressing a P0891 code can vary depending on the specific cause of the issue and the extent of the repairs needed. In general, the cost of replacing a TCM power relay or repairing wiring issues can range from $200 to $500, including parts and labor. However, additional costs may apply if the TCM needs to be replaced or reprogrammed. It's advisable to consult with a qualified mechanic or auto repair shop for a more accurate cost estimate based on the vehicle's make and model, as well as the severity of the problem. Keep in mind that labor rates can vary, so it's recommended to inquire about local rates before proceeding with the repairs.

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Code P0891 Information for Specific Makes

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0891 Code

1. What are the common symptoms of OBDII code P0891 (TCM Power Relay Sense Circuit High)?

The common symptoms of code P0891 include transmission shifting issues, poor fuel economy, and the illumination of the Check Engine Light.

2. What usually causes OBDII code P0891 to trigger?

Code P0891 is typically triggered by a malfunction in the transmission control module (TCM) power relay sense circuit, which can be caused by a faulty relay, wiring issues, or a problem with the TCM itself.

3. How can I diagnose the source of OBDII code P0891?

To diagnose the source of code P0891, you can start by checking the TCM power relay, inspecting the wiring harness for any damage or loose connections, and testing the TCM for proper functionality using a scan tool.

4. Can I continue driving my vehicle with OBDII code P0891 present?

It is not recommended to continue driving your vehicle with code P0891 present, as it can lead to further transmission problems and potential damage if left unaddressed.

5. How serious is OBDII code P0891 (TCM Power Relay Sense Circuit High)?

Code P0891 should be taken seriously as it can affect the performance and reliability of your vehicle's transmission system if not repaired promptly.

6. Are there any DIY repair tips for fixing OBDII code P0891?

While some may attempt to replace the TCM power relay themselves, it is recommended to consult a professional mechanic for proper diagnosis and repair to ensure the issue is resolved correctly.

7. How much does it typically cost to repair OBDII code P0891?

The cost of repairing OBDII code P0891 can vary depending on the underlying cause, but it may range from $200 to $500 or more, including parts and labor.

8. Can resetting the OBDII code P0891 on my own solve the issue?

Resetting the code may temporarily turn off the Check Engine Light, but it will not fix the underlying problem causing code P0891 to trigger in the first place.

9. Will OBDII code P0891 cause my vehicle to fail an emissions test?

Yes, code P0891 can cause your vehicle to fail an emissions test due to its impact on the transmission system, which is an important component for emission control.

10. How can I prevent OBDII code P0891 from recurring in the future?

Regular maintenance of your vehicle's transmission system, including checking the TCM power relay and wiring, can help prevent the recurrence of OBDII code P0891.

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