What Does P0802 Mean?
The Transmission Control System MIL Request Circuit is open or malfunctioning. This circuit allows the TCM to communicate with the PCM to request illumination of the check engine light when a transmission-related fault is detected. An open circuit means the TCM cannot properly signal the PCM about transmission problems, potentially masking other transmission faults.
Common Causes
35%
Open wiring between TCM and PCM MIL request line
25%
Corroded or damaged connector at TCM or PCM
20%
Faulty Transmission Control Module (TCM)
12%
PCM internal MIL request circuit fault
8%
Blown fuse in TCM power supply circuit
Diagnostic Steps
1
Check the TCM power supply fuse and verify TCM has proper power and ground with a multimeter.
2
Inspect both the TCM and PCM connectors for bent, pushed-back, or corroded pins on the MIL request circuit.
3
Measure continuity of the MIL request wire between TCM pin and PCM pin using the vehicle wiring diagram.
4
Check for CAN bus communication codes (U-codes) that might indicate a broader communication breakdown between modules.
5
Verify TCM is communicating properly by reading live transmission data — if no data is available, the TCM may be non-functional.
Estimated Repair Cost
$100 - $900
Parts + labor, varies by vehicle and location
The Transmission Control System MIL Request Circuit is open or malfunctioning. This circuit allows the TCM to communicate with the PCM to request illumination of the check engine light when a transmission-related fault is detected. An open circuit means the TCM cannot properly signal the PCM about t...
The most common cause of P0802 (Transmission Control System MIL Request Circuit / Open) is: Open wiring between TCM and PCM MIL request line
Typical repair costs for P0802 range from $100 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle can be driven, but this fault may mask other transmission problems since the TCM cannot request the MIL. Have the vehicle inspected soon — there may be underlying transmission faults that are not being reported to the driver.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0802 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Control System
Difficulty
Type
Generic (SAE)
Recommended Tools
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