P2A46: Alternative Fuel Tank C Pressure Sensor Circuit

What it means

The AFCM detects a generic fault on the pressure sensor of alternative fuel tank C. Tank pressure cannot be monitored reliably.

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 alternative fuel control module (AFCM) uses the pressure sensor for alternative fuel tank C to track pressure in that tank. This code sets when the module detects a fault in the sensor circuit that prevents it from monitoring tank C pressure reliably.

Common causes

Most likely first.

1. Pressure sensor failed
2. Wiring or connector fault

Symptoms

• Check-engine light
• Alternative-fuel warning light
• Inaccurate tank pressure or fuel-level indication

How to diagnose it

1. Record freeze-frame data and check live pressure readings for tank C to see whether the signal is missing, fixed, or implausible.
2. Inspect tank C's pressure-sensor connector and nearby wiring for loose fit, corrosion, damage, or chafing.
3. Check the sensor's power, ground, and signal circuits against the manufacturer's wiring information.
4. Measure the signal at the sensor and AFCM to locate an open, short, or poor connection.
5. If wiring and connections pass, test the tank C pressure sensor to the manufacturer's specification and replace it if it fails.

Common fixes

• Reconnect or clean the tank C pressure-sensor connector and repair damaged wiring.
• Repair an open, short, or poor ground in the tank C sensor circuit.
• Replace the tank C pressure sensor if its output fails the manufacturer's test.

Can I keep driving?

You may be able to drive if the vehicle runs normally, but tank C pressure and remaining-fuel indications may be unreliable and alternative-fuel operation may be limited. Avoid relying on the displayed range; switch fuels only as the vehicle's instructions allow.