What does it mean?
The module expects the pressure signal from cylinder 2 to be continuous and to follow the piston smoothly through every stroke, with no steps or gaps between samples. This code is stored when the signal momentarily vanishes, jumps to a value that combustion cannot produce, or becomes noisy and then settles back to normal. Because the disturbance is temporary, the circuit is not permanently broken; something in the connection or in the sensor is unstable under vibration, heat or load. Each interruption costs the module its combustion feedback for that cylinder for a short time, which the driver often notices as a brief change in running. Faults with this signature can set on one journey and stay silent on the next, so the diagnosis has to focus on reproducing the condition.
Symptoms
- MIL (check engine lamp) on, often only after the disturbance has occurred on several trips
- Momentary roughness or a brief stumble that clears without any driver action
- Idle that becomes uneven for a few seconds and then settles again
- Random small hesitations under acceleration with no repeatable pattern
- Combustion noise on diesel applications that changes now and then
- Occasional short lived power reduction that disappears after a restart
Likely causes
- Sensor connector not fully latched or a terminal that has lost its spring tension
- Wire in the cylinder 2 branch chafed against the head or a bracket, touching only when the engine rocks
- Oil or moisture entering the connector and creating an unstable leakage path
- Sensing element breaking down internally and producing noise as it heats up
- High resistance in the shared five volt reference or low reference, which disturbs the signal under load
- Harness rerouted or clipped incorrectly after previous work, allowing interference from injector or glow plug switching
- Loose sensor or a failing seal letting the element move slightly in its bore
How to fix it
- Read the freeze frame and note the coolant temperature, engine speed and load at which the events cluster
- Inspect the connector for a broken lock, loose terminals, oil contamination and a hardened seal, then check the harness for rub points along the head
- Record the sensor signal on a scope or graphing meter while wiggle testing the sensor, the harness branch and the module connector
- Monitor the five volt reference and the low reference during the same test, since an unstable reference upsets several sensors at once
- Take a live data recording on a road test that reproduces the freeze frame conditions and look for dropouts synchronised with bumps or throttle changes
- Repair the loose or damaged connection, or renew the sensor once it is proven to be the source, refitting with a new seal at the specified torque
- Clear the memory and confirm across several heat cycles and a mixed drive that the signal remains stable