The P1406 diagnostic trouble code is a manufacturer-specific powertrain code. Its exact definition depends heavily on the vehicle make, typically pointing to an EGR position sensor fault or a DPFE sensor hose issue.
Because this code targets different emissions components across manufacturers, the exact vehicle application must be verified before diagnosis. The code alone does not prove a specific component has failed without proper testing.
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Key Takeaways
- P1406 is a manufacturer-specific powertrain code with differing definitions depending on the vehicle make.
- On GM and Honda applications, it typically indicates an EGR valve position sensor circuit or performance fault.
- On Ford applications, it points to a Differential Pressure Feedback EGR (DPFE) sensor downstream hose issue.
- Diagnosis requires verifying the exact factory definition and testing the relevant sensor circuit or vacuum hoses.
- Repairs depend on the confirmed root cause and may involve replacing a sensor, clearing carbon buildup, or fixing a hose.
P1406 Code Description and Implications
The P1406 code indicates that a control module has detected a specific fault within the Exhaust Gas Recirculation (EGR) auxiliary emissions system. Because it is a manufacturer-specific code, the exact monitored component varies significantly by brand.
Some GM and Honda applications: P1406 indicates an EGR Valve Position Sensor Circuit or Performance fault. The PCM detects the EGR valve pintle position signal is out of range or does not match the commanded position.
Certain Ford applications: The code indicates a DPFE Sensor Downstream Hose Off or Plugged fault. The PCM detects an abnormal pressure differential, indicating the downstream hose to the DPFE sensor is disconnected, cracked, or blocked.
Common Causes of the P1406 Code
Because P1406 applies to different systems across different brands, the root cause depends on the verified vehicle application.
GM and Honda Causes: A failed EGR position sensor (often integrated into the EGR valve), carbon buildup restricting the EGR valve pintle, damaged wiring, or poor electrical connections at the sensor or PCM.
Ford Causes: A cracked, melted, or disconnected downstream DPFE hose, a failed DPFE sensor, or carbon buildup blocking the EGR tube orifice, preventing accurate differential pressure readings.
Symptoms Associated With P1406
When the control module detects a critical emissions fault, it illuminates a warning light and may alter engine operation.
Warning Lights: The Check Engine Light will illuminate on the dashboard.
Drivability: Rough idling, engine hesitation, stalling, or failed emissions tests due to improper EGR flow. On Ford applications, a rough idle or hesitation under load is common if the DPFE hose is melted.
Diagnosing the P1406 Trouble Code
Accurate diagnosis begins by verifying the exact vehicle application and reviewing manufacturer-specific service information.
For GM and Honda applications: Inspect the EGR valve and position sensor wiring. Command the EGR valve open and closed using a scan tool while monitoring the position sensor PID. Check for carbon binding the valve.
For Ford applications: Visually inspect the two hoses connected to the DPFE sensor. The downstream hose is prone to melting. Check for blockages in the EGR tube. Test the DPFE sensor voltage against specifications.
Repairing the P1406 Issue
Repairs must follow the confirmed root cause identified during diagnosis.
GM and Honda Repairs: Clean carbon deposits from the EGR valve passages. If the valve or internal position sensor fails electrical or mechanical testing, replace the EGR valve assembly. Repair any damaged wiring.
Ford Repairs: Replace any melted, cracked, or disconnected DPFE hoses using high-temperature silicone hose. If the hoses are intact but the sensor fails testing, replace the DPFE sensor. Clear carbon from the EGR orifices.
Cost Considerations for P1406 Repairs
Cost depends on diagnostic time, component accessibility, required parts, programming requirements, and labor.
Replacing a DPFE hose is inexpensive, while replacing an entire EGR valve assembly requires more parts cost and labor. Tracking down an intermittent wiring fault requires additional diagnostic time.
Prevention Strategies for Future Occurrences
Using high-temperature silicone hoses instead of standard rubber for DPFE applications can prevent future melting on Ford vehicles.
Addressing engine oil consumption or rich running conditions can help reduce excessive carbon buildup in the EGR passages across all applicable vehicles.
Troubleshooting Tips and Best Practices
Follow these practices to avoid misdiagnosis and ensure accurate repairs.
Do not assume the EGR valve is dead on GM applications: Carbon buildup frequently binds the pintle, causing a position error. Clean the valve and passages before replacing the entire assembly.
Check the downstream hose on Ford applications: The hose closest to the exhaust side of the EGR tube frequently melts from extreme heat, causing a false pressure reading.
Verify your definition: When researching this trouble code, always confirm whether your specific vehicle uses the EGR position sensor or DPFE hose definition before ordering parts.
More OBD-II Codes
| P1399 | P1400 | P1401 | P1403 |
| P1404 | P1405 | P1407 | P1408 |
| P1409 | P1410 | P1415 | P1416 |
| P1151 | P1174 | P1186 | P1188 |
| P1397 | P1478 | P1487 | P1488 |
| P0171 | P0174 | P0300 | P0420 |
Frequently Asked Questions
Is P1406 a generic or manufacturer-specific code?
No. P1406 is a manufacturer-specific powertrain code. Its definition varies significantly by brand, indicating an EGR position sensor fault or a DPFE sensor hose issue.
Can I drive my vehicle with a P1406 code?
The vehicle typically remains drivable. However, improper EGR flow can cause rough idling, hesitation, or increased emissions, and the vehicle will likely fail an emissions test.
Will disconnecting the battery clear the P1406 code?
Disconnecting the battery might temporarily clear the code. However, it does not repair the underlying failed sensor, melted hose, or carbon buildup, and the code will return.
Can a melted hose cause a P1406 code?
Yes. On Ford applications where P1406 indicates a DPFE sensor downstream hose fault, a melted or disconnected silicone hose is a frequent cause of the pressure reading error.
Does P1406 affect the transmission?
No. The P1406 code relates strictly to the auxiliary emissions control and EGR system. It does not directly affect the operation of the automatic or manual transmission.
What Should You Do About the P1406 Code?
When a P1406 code appears, confirm the exact factory definition for your specific vehicle make and model. Because this code targets entirely different emissions components depending on the manufacturer, applying the wrong diagnostic path will lead to misdiagnosis.
Follow the applicable manufacturer diagnostic procedure to test the relevant system and components. Once the root cause is confirmed, complete the necessary electrical repairs, hose replacements, or carbon cleaning before returning the vehicle to normal service.
