P20A8 code meaning
Reductant Injection Air Pressure Control Valve Circuit Low
Powertrain system Generic code P20xx codes Check engine light
What P20A8 means
P20A8 says the air pressure control valve's drive circuit sits at too low a level, which normally means a short to ground. Depending on whether the valve is switched on the high or the low side, this either stops the valve from opening at all or energizes it without command. In both cases the controller loses control of the atomizing air. The fault differs from P20A6, where the circuit is interrupted, and from P20A9, a short toward battery voltage. No manufacturer documents P20A8 publicly. For the comparable valves of its air-assisted system, Deutz lists the high-side short to ground as P2060 on the air pump or supply valve and as P1061 on the air switching valve. CARB requires such circuit checks on every electrical component of the SCR system. A chafed harness on the frame rail is the classic finding.
P20A8 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P20A8
- MIL or SCR lamp on
- Blown fuse possible on high-side switched valves
- Dosing stopped, derate on trucks
Common causes of P20A8
- Most likelyHarness chafed through to ground along the frame
- PossibleSolenoid coil shorted to the valve body
- PossibleWater in the connector creating a path to ground
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant air pressure control valve
What each part of P20A8 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 0 | Area: fuel and air metering and auxiliary emission controls. |
| A8 | The exact fault in that area. |
What to do next
- Note P20A8 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P20A8
What does P20A8 mean?
P20A8 means "Reductant Injection Air Pressure Control Valve Circuit Low". P20A8 says the air pressure control valve's drive circuit sits at too low a level, which normally means a short to ground. It is a generic code, so it means the same on every make.
Is it safe to drive with P20A8?
Drive gently and only to a workshop. With P20A8 the car can go into limp mode (reduced power) to protect itself.
Will P20A8 fail an emissions test?
Yes, it can. P20A8 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P20A8 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will P20A8 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.