Exhaust Brake Actuator Control Circuit Voltage Below Normal / Open
Low voltage or open on the exhaust brake actuator is a wiring, fuse, or actuator problem. Prove continuity and voltage under command.
Fault Overview
Voltage below normal or open-circuit condition on the exhaust brake actuator control. The ECM detects the circuit does not reach the expected voltage or current when commanded.
Engine & Platform Coverage
Symptoms
- •Exhaust brake low voltage
- •Exhaust brake open circuit
- •Exhaust brake inoperative
- •Actuator no movement
Possible Causes
- 1.Open or short-to-ground on control wire
- 2.Failed open actuator
- 3.Blown fuse
- 4.High-resistance connection
- 5.Poor ground
- 6.Heat-damaged wiring creating open
Diagnostic Flow — FSM Sequence
AI Diesel Tech enforces this evidence-gate sequence. Each gate must pass before advancing.
5 steps locked behind Technician Mode- 1Step 1 — Measure Control Voltage Under Command: Measure control voltage when the brake is commanded. No voltage confirms an open or power supply issue.
- 2Step 2 — Check Actuator Resistance and Continuity: Measure actuator resistance and continuity. An open actuator will show infinite resistance.
- 3Step 3 — Short-to-Ground and Open Tests on Wiring: Perform short-to-ground and open tests on the control and power wires with the actuator disconnected.
- 4Step 4 — Verify Fuse and Power Feed: Check all fuses in the exhaust brake circuit and verify power feed voltage.
- 5Step 5 — Command and Observe Response: Command the brake and observe mechanical response after any repairs.
- 6Step 6 — Inspect for Heat Damage: Inspect the harness near the exhaust brake for heat-related opens, which are the dominant failure mode on this circuit.
Unlock the full evidence-gated diagnostic sequence, DVOM test steps, and repair procedures in Technician Mode.
Repair Steps
2 steps locked- 1Repair or replace heat-damaged harness.
- 2Replace failed actuator.
- 3Restore connector and ground.
- 4Replace blown fuse and identify root cause.
Unlock full diagnostic steps, DVOM tests, and repair procedures.
Full Diagnostic Access
Verification steps, preventative measures, severity guidance, and legacy comparison are available in Technician Mode.
Start Diagnosing This Fault Now
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Summary
Low voltage or open on the exhaust brake actuator is a wiring, fuse, or actuator problem. Prove continuity and voltage under command.