What is OBD-II Code P0891 – TCM Power Relay Sense Circuit High



What is OBD-II Code P0891 – TCM Power Relay Sense Circuit High

Your car’s engine computer system is fitted with numerous sensors that all work together to ensure that the vehicle runs efficiently. When the system detects an error in any of its components, it turns on the Check Engine Light (CEL). Anytime the CEL comes on, the system stores a diagnostic trouble code (DTC) that can be read through an OBD-II scanner. One of the many DTCs that your scanner can detect is OBD-II Code P0891 – TCM Power Relay Sense Circuit High. This code is usually triggered when there’s an electrical fault specifically in the Transmission Control Module (TCM) relay circuit. This article will explain what OBD-II Code P0891 means, its symptoms, causes, and repair procedures.

What is OBD-II Code P0891

OBD-II Code P0891 is a generic trouble code that indicates that the engine control module (ECM) or transmission control module (TCM) has detected a high voltage in the TCM power relay sense circuit. The TCM power relay sense circuit is responsible for monitoring the voltage that’s supplied to the TCM. If the system detects that the voltage is too high, it triggers OBD-II Code P0891. The check engine light will come on and remain lit until the problem is fixed.

Symptoms of OBD-II Code P0891

The symptoms of OBD-II Code P0891 may differ from one vehicle to another. However, some symptoms are common and may include:

– Check engine light comes on
– Reduced fuel efficiency
– Difficulty in shifting gears
– Transmission stuck in one gear
– Harsh shifting

These symptoms are not conclusive, and there may be other reasons why these symptoms might occur. To determine the exact cause of the symptoms, it’s always best to use an OBD-II scanner to read the codes and diagnose the problem accurately.

Causes of OBD-II Code P0891

There are several reasons why OBD-II Code P0891 may be triggered. These reasons include:

1. Faulty TCM power relay
2. Damaged wiring in the TCM power relay circuit
3. Faulty TCM ground circuit
4. Short circuit in TCM power relay circuit
5. Damaged TCM itself

Repairing OBD-II Code P0891

The repair procedures for OBD-II Code P0891 will depend on the underlying cause. Here are some repair procedures that are commonly used:

1. Check the TCM Power Relay

The first step in fixing OBD-II Code P0891 is to check the TCM power relay. You can do this by using a voltmeter to test the voltage in the circuit. If the voltage is too high or too low, then it’s likely that the relay is faulty. If this is the case, replace the TCM power relay with a new one.

2. Check the Wiring

The next step is to check the wiring in the TCM power relay circuit. Inspect the wires to make sure that they are not damaged, corroded, or broken. If there are any issues with the wiring, repair or replace the wires as needed.

3. Check the TCM Ground Circuit

The next step is to check the TCM ground circuit. Use a voltmeter to check the resistance between the TCM and the battery’s negative terminal. If the resistance is high, it’s likely that there’s an issue with the ground circuit. Clean or replace the ground circuit to ensure that the TCM has a proper ground connection.

4. Check for Short Circuits

If the previous steps don’t resolve the problem, it’s best to check for short circuits in the TCM power relay circuit. Check the circuit for any signs of damage or short circuits. If there’s a short circuit, fix it before proceeding.

5. Replace the TCM

If all the previous steps fail to resolve the issue, then it’s likely that the TCM itself is damaged. In this case, you will need to replace the TCM with a new one.

Frequently Asked Questions

1. What causes OBD-II Code P0891?

OBD-II Code P0891 can be triggered by a faulty TCM power relay, damaged wiring in the TCM power relay circuit, faulty TCM ground circuit, short circuit in TCM power relay circuit, or a damaged TCM itself.

2. What are the symptoms of OBD-II Code P0891?

Symptoms of OBD-II Code P0891 may include a check engine light comes on, reduced fuel efficiency, difficulty in shifting gears, transmission stuck in one gear, or harsh shifting.

3. How do I repair OBD-II Code P0891?

Repair procedures for OBD-II Code P0891 will depend on the underlying cause, you will need to check the TCM power relay, check the wiring, check the TCM ground circuit, check for short circuits, and replace the TCM if necessary.

4. Can I still drive my car if OBD-II Code P0891 is triggered?

It’s generally safe to drive your vehicle if OBD-II Code P0891 is triggered, but it’s always best to fix the issue as soon as possible to avoid more severe problems in the future.

5. How do I clear OBD-II Code P0891?

You can clear OBD-II Code P0891 by using an OBD-II scanner, but it’s best to fix the underlying issue first before clearing the code.

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