P1404
Exhaust Gas Recirculation (EGR) Closed Position Performance
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The P1404 code is a very common GM-specific code that means the EGR (Exhaust Gas Recirculation) valve is not fully closing when the PCM commands it to. The PCM expects the EGR position sensor voltage to drop below 0.29 volts when the valve is closed, and this code sets when it stays above that threshold.
The overwhelming cause of this code on GM vehicles is carbon buildup. Over time, exhaust soot and carbon deposits accumulate on the EGR valve's pintle and seat, creating a physical obstruction that prevents complete closure. The good news is that in many cases, removing the EGR valve and cleaning it with carburetor cleaner and a brush can resolve the issue without needing to buy a new part.
If cleaning doesn't fix it, the EGR valve itself may need replacement. Aftermarket EGR valves for GM trucks and cars typically cost $40–$80. This is a straightforward DIY repair — the EGR valve is usually held on by two bolts on top of the intake manifold and has one electrical connector. While the vehicle is safe to drive, a stuck-open EGR can cause rough idle, stalling, and will cause an emissions test failure.
Severity
Symptoms
- •Rough or erratic idle, especially when the engine is warm
- •Engine may stall at idle or when coming to a stop
- •Pinging or knocking noise during acceleration
- •Reduced fuel economy
- •Occasional failed emissions inspection
Likely Causes
By far the most common cause — exhaust carbon deposits accumulate on the EGR valve pintle and its seat, physically preventing the valve from closing all the way. The position sensor reports the pintle is still slightly open when the PCM commands it closed.
The EGR valve's internal components — the pintle, spring, or position sensor — have worn out or failed, preventing proper operation or accurate position reporting.
The potentiometer that reports pintle position to the PCM may have a dead spot or drift, causing it to report voltage above the 0.29V closed-position threshold even when the valve is mechanically closed.
Corroded, damaged, or loose connections at the EGR valve electrical connector can cause incorrect voltage readings at the PCM.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Remove and clean carbon deposits from the EGR valve pintle and seat
- Replace the EGR valve if cleaning doesn't resolve the issue
- Inspect and clean the EGR position sensor connector
- Clean carbon from the EGR passages in the intake manifold