U3572: Stack Outlet Coolant Temperature Sensor 2 Circuit

What it means

Generic fault on coolant temperature sensor 2 at the fuel cell stack outlet (used to monitor stack thermal output).

At a glance

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

How it works

Stack outlet coolant temperature sensor 2 measures coolant temperature leaving the fuel cell stack, providing a second outlet-temperature signal for thermal monitoring. This code identifies a fault associated specifically with sensor 2's circuit or data; CAN routing or termination faults can also disrupt the signal.

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. Record freeze-frame data and scan all modules for communication codes, checking whether the fault is specific to outlet sensor 2.
2. Compare sensor 2's live outlet temperature with sensor 1 and the stack inlet reading for a missing or implausible value.
3. Inspect sensor 2's outlet connector and wiring for corrosion, a loose fit, abrasion, or other damage.
4. Test sensor 2 and its circuit using service information and the manufacturer's specification.
5. If other modules also show communication faults, inspect gateway routing and CAN wiring and termination to the manufacturer's specification.

Common fixes

• Reconnect or repair the sensor 2 connector or damaged wiring.
• Replace a faulty stack outlet coolant temperature sensor 2.
• Correct a gateway fault that is routing the sensor data incorrectly.
• Repair CAN network wiring or replace an out-of-spec terminating resistor.

Can I keep driving?

Limit driving if warnings or reduced power occur, since the stack's outlet temperature monitoring may be incomplete. Stop if the fuel cell system shuts down or a stop warning appears.