OBD-II Code P0474 — What It Means & How to Fix It

What Does This Error Mean?

P0474 means the exhaust pressure sensor signal is intermittent — it cuts in and out rather than staying steady. The computer detected that the sensor voltage keeps dropping or spiking unexpectedly. Intermittent codes are typically caused by loose connectors, damaged wiring, or a sensor that is starting to fail. You may notice occasional rough running, brief power loss, or the check engine light that comes and goes.

Affected Models

Diesel trucks 2003 and newer
Ford F-250/F-350/F-450 Power Stroke diesels
Dodge/RAM Cummins diesel pickups
GM Duramax diesel trucks
Diesel vans and medium-duty vehicles

Common Causes

Loose or intermittently connecting wiring connector at the sensor
Chafed or partially broken wire in the harness that makes contact only sometimes
Exhaust pressure sensor starting to fail — works when cold but fails when hot, or vice versa
Sensor port or tube partially blocked with soot, causing fluctuating readings
Vibration in the exhaust system causing the wiring to lose connection temporarily

How to Fix It

Wiggle the wiring connector at the exhaust pressure sensor firmly by hand while the engine is running. If the engine bogs, runs rough, or the check engine light flickers, the connector is the problem.

This is the quickest test for an intermittent connector issue. If wiggling it causes a symptom, you have found the fault.
Unplug the connector and inspect the pins. Look for bent, pushed-back, or corroded terminals. Use electrical contact cleaner and a pin repair tool to clean and re-tension any loose pins.

Connector repair kits are available at auto parts stores. A properly seated pin fixes most intermittent sensor codes.
Trace the wiring harness from the sensor back toward the PCM. Look for any area where the harness flexes, rubs on metal, or passes near the exhaust. Flex the harness by hand while watching the scan tool sensor data.

The sensor data reading should be rock-steady. If it jumps or drops to zero when you flex a section of harness, you have found the damaged spot.
Clean out the sensor port and tube with compressed air or a thin wire. Soot buildup can cause the sensor to read inconsistently as it partially clears and re-clogs.

On high-mileage diesels, this step alone sometimes resolves intermittent exhaust sensor codes.
If no wiring fault is found and the port is clean, replace the sensor. Intermittent sensor failures are common as sensors age. Clear the code and verify the repair over several drive cycles.

An intermittent failure is hard to confirm without replacing the sensor, especially once all wiring checks out.

When to Call a Professional

Intermittent faults are the hardest to find because they come and go. A shop with an oscilloscope can watch the sensor signal in real time and catch dropouts. Expect $100 to $200 for diagnosis and another $50 to $100 for the sensor if needed.

Frequently Asked Questions

Why does the check engine light come on and off with P0474?

P0474 is an intermittent fault, which means the sensor only misbehaves sometimes. The PCM turns on the check engine light when it detects the problem, then turns it off if the sensor behaves normally for a set number of drive cycles. The underlying problem is still there — it just isn't misbehaving at that moment.

Why are intermittent codes harder to fix than steady ones?

With a steady fault, the problem is always present and easy to measure. With an intermittent fault, you have to catch it in the act. Heat, cold, vibration, and moisture can all trigger intermittent faults at unpredictable times. This is why wiggle testing and live scan tool data are essential for these codes.

Can extreme cold or heat cause P0474?

Yes. Sensor connectors can loosen slightly as metal expands and contracts with temperature changes. A sensor that works in warm weather may fail in cold weather due to a slightly loose pin. If P0474 appears only when temperatures are extreme, check the connector and terminals carefully.