Transmission Control System MIL Request Circuit/Open
The P0802 code indicates a problem in the circuit that requests the Malfunction Indicator Lamp (MIL) to illuminate on the dashboard. This circuit is controlled by the Transmission Control Module (TCM) and communicates with the Powertrain Control Module (PCM) to turn on the check engine light when a transmission fault is detected. An open or short in this circuit prevents the MIL from activating, potentially hiding transmission issues.
1. Symptoms You Will Notice
- Check Engine Light (MIL) does not illuminate when key is turned on
- Transmission shifting issues or harsh shifts
- Vehicle fails emissions test due to MIL not functioning
- Other transmission-related codes may be stored
2. Most Common Causes
- Open or short in the MIL request circuit wiring
- Faulty Transmission Control Module (TCM)
- Faulty Powertrain Control Module (PCM)
- Corroded or damaged connectors in the circuit
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect the MIL request circuit wiring and connectors for damage, corrosion, or loose connections.
Step 3: Test the circuit continuity between TCM and PCM using a multimeter.
Step 4: Check for proper voltage and ground at the TCM and PCM connectors.
Step 5: If wiring is intact, suspect a faulty TCM or PCM and perform further module testing.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended because the MIL may not illuminate for serious transmission faults, leading to potential damage. Have it diagnosed promptly.
How much does it cost to fix?▼
Typically $50-$150 for diagnosis and repair, but costs can vary if a module replacement is needed.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.