What it means
The control module monitors the exhaust-brake input signal and sets this code when the signal is intermittent or erratic instead of stable. The code indicates an input-circuit problem but does not identify its cause.
At a glance
- Usually lights the check-engine light
How it works
The exhaust-brake input circuit reports the driver’s request to the control module. This code sets when that signal changes erratically or drops in and out instead of remaining stable as the control is operated or released.
Common causes
Most likely first.
- Intermittent contact at connector
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Exhaust brake may engage inconsistently
- Exhaust-brake input may come and go
How to diagnose it
- Review freeze-frame data and watch live exhaust-brake input status while operating the driver control several times.
- Inspect the input connector for a loose fit, corrosion, or damaged pins that may lose contact with vibration.
- Check the harness routing near vibrating components for rubbing, tension, or damaged insulation.
- Use the wiring diagram to test circuit continuity while gently moving the connector and harness to find intermittent contact.
- If the wiring remains stable, check the switch or sensor output for dropouts against the manufacturer’s specification.
Common fixes
- Reseat and secure the exhaust-brake input connector.
- Repair damaged harness insulation and reroute or secure wiring away from vibration.
- Clean or repair corroded connector terminals.
- Replace a switch or input sensor that produces intermittent output despite a sound circuit.
Can I keep driving?
The exhaust brake may engage inconsistently, so do not rely on it to control speed downhill. Use appropriate gearing and service braking, and avoid demanding descents until the fault is repaired.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.