What it means
The inlet pressure sensor circuit signal for the alternative fuel rail pressure regulator is lower than expected.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The regulator inlet pressure sensor sends a signal representing incoming alternative-fuel rail pressure to the control module. This circuit-low code sets when that signal falls below the expected range, so the module cannot trust the pressure reading and may restrict alternative-fuel operation.
Common causes
Most likely first.
- Signal wire shorted to ground
- Internal sensor short
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine or alternative-fuel system warning light
- Rough running or hesitation on alternative fuel
- Alternative-fuel operation may be limited
How to diagnose it
- Check freeze-frame and live inlet-pressure data to confirm a low signal and relate it to any rough running or hesitation.
- Inspect the sensor connector and harness for corrosion, damaged insulation, or a signal wire shorted to ground.
- Check the sensor ground and connector terminals for poor contact or excessive resistance.
- With power isolated as required by service information, test the signal circuit for a short to ground and inspect circuit continuity.
- Compare sensor output, supply, and ground readings with the manufacturer's specification to distinguish a sensor short from a wiring fault.
Common fixes
- Clean and secure corroded or loose pressure sensor terminals.
- Repair a signal wire shorted to ground or damaged harness insulation.
- Restore a poor sensor ground or connector connection.
- Replace the inlet pressure sensor if it is internally shorted and fails the manufacturer's checks.
Can I keep driving?
The pressure reading may be wrong, causing rough running or hesitation, and alternative-fuel operation may be limited. Avoid hard acceleration; if the engine runs unpredictably, switch away from alternative fuel if possible or stop safely.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.