P2A4C: Alternative Fuel Temperature Sensor Range/Performance

What it means

The alternative fuel temperature signal does not match plausibility checks against ambient and fuel-rail temperatures. Sensor drift.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The AFCM checks whether the alternative fuel temperature reading makes sense alongside ambient and fuel-rail temperatures. This code sets when the signal is readable but fails those plausibility checks, which can indicate sensor drift or a sensor displaced from the fuel path.

Common causes

Most likely first.

1. Sensor characteristic drifted
2. Sensor mounting displaced from fluid path
3. Sensor element aged beyond calibration window

Symptoms

• Check-engine or alternative-fuel system warning light
• Alternative-fuel operation may be limited
• Reduced fuel economy

How to diagnose it

1. Save freeze-frame data and compare live alternative-fuel temperature with ambient and fuel-rail readings, especially before the fuel system warms.
2. Check whether the temperature reading changes plausibly as the vehicle and fuel system warm.
3. Inspect the sensor mounting to see whether it has shifted away from its intended position in the fluid path.
4. Inspect the connector and wiring for poor contact or damage that could distort the reading.
5. If mounting and wiring are sound, test the sensor against the manufacturer's specification for drift.

Common fixes

• Reposition and secure the sensor correctly if it has moved from the fuel path.
• Clean or repair a poor connector contact or damaged temperature-sensor wiring.
• Replace the sensor if its temperature response remains outside the manufacturer's specification.

Can I keep driving?

The vehicle may remain drivable if it runs normally, but alternative-fuel operation can be limited and fuel economy may fall. Avoid continued alternative-fuel use if the system warns of a fault or the engine begins running poorly.