What Does P086A Mean?
This DTC code is listed as ISO/SAE Reserved, meaning it has been allocated in the OBD-II standard but does not yet have a universally published definition. Some manufacturers may use this code for proprietary transmission-related diagnostics. The code appearing may indicate a TCM firmware issue or a manufacturer-specific condition.
Common Causes
35%
Manufacturer-specific transmission control issue
25%
TCM firmware or calibration out of date
20%
Communication error between TCM and ECM
12%
Aftermarket tuning or programming conflict
8%
Intermittent electrical fault in transmission harness
Diagnostic Steps
1
Check for any available Technical Service Bulletins (TSBs) from the vehicle manufacturer regarding this specific code.
2
Verify TCM software version and check if a calibration update is available from the manufacturer.
3
Monitor freeze frame data and note all other codes that set simultaneously — this may provide context for the reserved code.
4
Inspect the transmission wiring harness and TCM connectors for damage, corrosion, or loose terminals.
5
If no other codes are present and the vehicle operates normally, clear the code and monitor for recurrence.
Estimated Repair Cost
$100 - $500
Parts + labor, varies by vehicle and location
This DTC code is listed as ISO/SAE Reserved, meaning it has been allocated in the OBD-II standard but does not yet have a universally published definition. Some manufacturers may use this code for proprietary transmission-related diagnostics. The code appearing may indicate a TCM firmware issue or a...
The most common cause of P086A (ISO/SAE Reserved) is: Manufacturer-specific transmission control issue
Typical repair costs for P086A range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Generally safe to drive if no drivability symptoms are present. Since this is a reserved code, consult a dealer or specialist familiar with your specific vehicle make for proper diagnosis.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P086A 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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