TCM Power Relay Control Circuit Low
The P0886 code indicates that the Transmission Control Module (TCM) has detected a low voltage condition in the power relay control circuit. This circuit supplies power to the TCM, and when voltage drops below the specified threshold, the TCM sets this code. Common causes include a faulty relay, wiring issues (shorts or opens), a weak battery, or a failing alternator. This can lead to transmission shifting problems, limp mode, or no start conditions.
1. Symptoms You Will Notice
- Transmission stuck in limp mode
- Harsh or erratic shifting
- Check Engine Light illuminated
- Possible no-start condition
2. Most Common Causes
- Faulty or damaged TCM power relay
- Relay control circuit shorted to ground
- Loose or corroded connections in the TCM relay circuit
- Blown or undersized TCM power fuse
- Internal TCM failure (rare but possible)
- Weak or undercharged battery
- Excessive resistance in the TCM power supply circuit
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Inspect the TCM power relay and its wiring for damage or corrosion.
Step 3: Test battery voltage and alternator output; ensure connections are clean and tight.
Step 4: Use a multimeter to check for voltage at the TCM relay control circuit; repair as needed.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The vehicle may enter limp mode, reducing speed and transmission performance, which can be dangerous in traffic.
How much does it cost to fix?▼
Typically $50-$150 for parts and labor, but costs can vary if extensive wiring repairs are needed.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.