U3576: Stack Differential Pressure Sensor Circuit

What it means

Generic fault on the differential pressure sensor across the fuel cell stack — measures the pressure drop between cathode and anode (used to detect membrane damage or flooding).

At a glance

• Usually lights the warning light of the system that lost communication
• The engine or gearbox may go into limp mode

How it works

The stack differential pressure sensor measures the pressure difference between the fuel cell stack's cathode and anode sides, information used to monitor stack operation and detect conditions such as flooding or membrane problems. This code indicates a fault associated with the sensor circuit or its data; CAN routing or termination faults can also interrupt the reading.

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 related communication and fuel cell pressure faults.
2. Review live differential-pressure data under the conditions shown in the freeze frame for missing or implausible readings.
3. Inspect the sensor connector, harness, and pressure connections for damage, loose fittings, blockage, or leaks.
4. Test the sensor and its electrical circuit using service information and the manufacturer's specification.
5. If multiple modules show communication faults, check gateway routing and CAN wiring and termination against the manufacturer's specification.

Common fixes

• Reconnect or repair a loose or damaged sensor connector or harness.
• Clear a blocked pressure connection or repair a leak, if inspection identifies one.
• Replace a faulty stack differential pressure sensor.
• Correct gateway routing or repair CAN network wiring or an out-of-spec terminating resistor.

Can I keep driving?

Because this reading supports fuel cell stack protection, avoid driving if the vehicle shows reduced power, stack warnings, or a shutdown warning. A faulty signal can prevent the system from identifying pressure conditions that may damage the stack.