P039A: The monitored pressure in cylinder 1 is too low.
Meaning, symptoms, causes and checks
The monitored pressure in cylinder 1 is too low. The definition does not provide a compression specification or identify the mechanical cause.
Affected system: Cylinder pressure and combustion monitoring
Symptoms
- Warning light may illuminate
- Related system function may be impaired
- Vehicle-specific symptoms vary
Possible causes
- Mechanical timing or operating issue, sensor or actuator fault, connector or wiring damage
- Related wiring, connector, power or ground fault
- Vehicle-specific mechanical or control issue
What to check
- Record stored and pending codes and freeze-frame data
- Record freeze-frame conditions; compare relevant live data and inspect mechanical operation, wiring and related fault codes before replacing parts.
- Confirm measured values against the vehicle service information
- Retest under the conditions that set the code
- Record freeze-frame conditions; compare relevant live data and inspect mechanical operation, wiring and related fault codes before replacing parts.
- Repair the verified cause and confirm the code does not return
Also written as: P039A-00, P039A00, PO39A (some scan tools add the fault-type byte, e.g. -00).