OBD-II code · Powertrain (generic)
P04A8 Exhaust Pressure Control Valve B Position Sensor Circuit Low
Same as P04A6 with the signal voltage below the plausible range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
Is it safe to drive with P04A8?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelySignal shorted to ground
- Less likelyConnector pins corroded - high contact resistance
- Less likelyHarness chafing through insulation
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.8–2 h
- Emissions test
- Likely to fail
- Parts involved
- Exhaust Pressure Position Sensor B
Related codes
- P04A5Exhaust Pressure Control Valve B Stuck Closed
- P04A6Exhaust Pressure Control Valve B Position Sensor Circuit
- P04A7Exhaust Pressure Control Valve B Position Sensor Circuit Range or Performance
- P04A9Exhaust Pressure Control Valve B Position Sensor Circuit High
- P04AAExhaust Pressure Control Valve B Position Sensor Circuit Intermittent or Erratic
- P04ABEVAP System Purge Control Valve B Circuit Open
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.