U355C: Charge Air Cooler Outlet Temperature Sensor Circuit

What it means

Generic fault on the charge air cooler outlet temperature sensor in the FCEV cathode supply path. A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp mode.

At a glance

• Usually lights the warning light of the system that lost communication

How it works

The charge air cooler outlet temperature sensor reports the temperature of air leaving the cooler in the fuel-cell cathode supply path. The control module monitors whether it can receive and use this sensor's data; this code is set when that communication or data path fails.

Common causes

Most likely first.

1. Sensor failed
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Use a scan tool to record freeze-frame data and check which modules report communication faults, because a group of faults can point to a network or gateway issue.
2. Check whether the charge air cooler outlet temperature reading is present and plausible compared with other temperature data under similar conditions.
3. Inspect the sensor connector and its wiring along the cooler outlet path for loose connections, corrosion, damage, or chafing.
4. Check the sensor's power, ground, and signal circuits against the manufacturer's specification to distinguish a wiring fault from a failed sensor.
5. If other modules also lose communication, have the gateway routing and CAN network, including its terminating resistance, checked to the manufacturer's specification.

Common fixes

• Reconnect or repair damaged wiring at the charge air cooler outlet temperature sensor.
• Clean or repair corroded sensor connector terminals.
• Replace the charge air cooler outlet temperature sensor if its circuit checks pass but its data remains faulty.
• Repair gateway or CAN network faults identified by network testing.

Can I keep driving?

If the vehicle shows reduced power, shutdown warnings, or other affected functions, stop in a safe place and avoid continued driving because the fuel-cell system may limit or lose operation. If only a warning is present and the vehicle behaves normally, arrange prompt diagnosis and avoid demanding operation.