P25D6

Code

Generic P — Powertrain

Exhaust Heat Exchanger Exhaust Bypass Valve A Position Sensor Stop Performance

Brand: Generic

Type: P — Powertrain

Views: UK: 31 EN: 41 RU: 33

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Faulty exhaust bypass valve position sensor (open, short, internal failure)
Damaged or corroded wiring or connectors to the sensor
Loss of reference voltage or ground to the sensor
Valve actuator seized, mechanically bound or obstructed
Failed bypass valve actuator (motor/solenoid) or internal linkage
Control module (ECU) driver or software fault

Symptoms

Check Engine Light (MIL) illuminated
Reduced exhaust heat exchanger performance or reduced heater effectiveness
Possible limp mode or reduced engine performance depending on strategy
Unusual exhaust noises or clanking if linkage is loose
Stored related fault codes for actuator control or position feedback

What to check

Read freeze frame and related codes with a capable scan tool; note conditions when code set
Visually inspect harness and connector at the exhaust heat exchanger bypass valve for damage, corrosion or overheating
Check for obvious mechanical binding of the bypass valve and linkage
Confirm engine/vehicle battery voltage is within normal range
Attempt to command the valve (open/close) with a scan tool while monitoring feedback

Signal parameters

Reference voltage to sensor: typically 5.0 V (±0.5 V) — confirm with manufacturer spec
Sensor signal voltage range: roughly 0.1–4.9 V depending on position (exact range depends on sensor type)
Signal should change smoothly when valve is moved or commanded; a fixed/stuck voltage indicates no movement or open/short
Expected sensor resistance (if potentiometer type): manufacturer-specific; check service data
Actuator current draw when commanded: should be within spec; excessive draw may indicate mechanical bind

Diagnostic algorithm

Retrieve all stored codes and freeze frame data. Record PID values for the bypass valve position and related parameters.
Perform a visual inspection of the valve assembly, wiring and connector. Repair or secure any damaged wiring or connectors.
With ignition ON (engine off), measure reference voltage and ground at the sensor connector. Verify reference voltage is present and stable.
Backprobe the sensor signal wire and monitor voltage while commanding the bypass valve open/close with a scan tool. Observe whether the signal changes and whether it follows commanded movement.
If the signal is fixed or absent, check continuity from the sensor connector to the ECM for open/short conditions. Repair any wiring faults.
If wiring and ECM connections are good but signal does not change, inspect the valve mechanically. Attempt to manually move the valve (safe, cool condition) to check for binding or mechanical damage.
Command the actuator and measure actuator power/ground and current draw. If actuator receives proper drive but does not move, suspect mechanical failure or seized actuator.
If wiring, actuator and mechanical operation are confirmed good, test/replace the position sensor. Re-test system operation after replacement.
If problem persists after sensor and actuator replacement, consider ECM driver fault or software; consult manufacturer service information for reprogramming or ECM testing.
Clear codes and perform road or operational test to confirm repair. Re-scan for returned codes.

Likely causes

Wiring connector corrosion at the valve harness
Sensor stuck due to soot/ash buildup or heat deformation
Open circuit in sensor signal or ground wire
Actuator failure preventing movement so sensor reading appears stopped
Intermittent reference voltage caused by damaged harness

Fault status

⚠️ Status

Position sensor for Exhaust Heat Exchanger Exhaust Bypass Valve A has stopped or is not providing valid position feedback. Control module detected no change or out-of-range feedback during commanded operation.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours