OBD-II Diagnostic Trouble Code
P1404 — EGR Closed Position Performance
P1404 is a manufacturer-specific code that commonly means the EGR valve position sensor reading in the closed position is outside the expected range, so the ECM thinks the valve is not fully closing or the sensor baseline has shifted. Meaning can vary by OEM.
Severity 3/5
Truck-relevant
Service this week
Severity
Service this week
EGR Closed Position Performance
Code
P1404
Category
Powertrain
Subsystem
Emissions
Truck-relevant
Yes
What this means for truckers
Service within a few days on a Cummins X15, Detroit DD15, PACCAR MX-13. Performance is likely degraded. Continuing to drive without service risks additional component damage.
Before you replace parts — try this first
P1404 on the Emissions system is most often carbon buildup keeping the egr valve from fully closing — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Rough idle, stumbling or stalling at idle, low power, possible derate and excess soot. Some trucks show only a check-engine light.
Common causes
- CommonCarbon buildup keeping the EGR valve from fully closing ($200–$800)
- OccasionalFaulty EGR position sensor ($200–$700)
- OccasionalWiring or connector fault ($100–$400)
- OccasionalFailed EGR valve or actuator ($600–$2200)
- RareECM fault ($500–$2000)
How to fix
Check EGR position at closed command with a scan tool
When to use: First step
Remove and clean the EGR valve and passages
When to use: When carbon is preventing closure
Check sensor wiring and connector
When to use: When readings are erratic
Replace the EGR valve assembly and perform any relearn
When to use: When cleaning does not fix it
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
Frequently Asked Questions
Can I drive with code P1404?
P1404 is severity 3 — plan service within a few days. Performance is likely degraded already (you may feel reduced power, harsher shifts, or slightly worse fuel economy). Continuing to drive risks additional damage to adjacent components.
How much does it cost to fix P1404 on a commercial truck?
Total repair cost ranges $100–$2200 depending on the root cause. The cheapest fix is usually the first one listed below — Carbon buildup keeping the EGR valve from fully closing — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P1404 fail a DOT inspection?
Yes — P1404 is an emissions-related code, and DOT inspectors check emissions compliance. An active emissions code with a check engine light can result in an out-of-service violation under FMCSA Part 393. The truck typically can't be moved until the code is cleared. Repeated emissions violations escalate to CSA scores.
What's the difference between P1404 and related codes?
P1404 is closely related to: P1410 (EVAP System Pressure Sensor), P1450 (Unable to Bleed Up Fuel Pressure), P1455 (EVAP System Leak (Gross Leak)). These codes share the same subsystem (emissions) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P1404 is set without the companions, the issue is more isolated.
How do I prevent P1404 from coming back after a repair?
For P1404 (EGR Closed Position Performance), prevention centers on the emissions system. Keep up with PM on the EGR system — clean the valve at 200K miles. Use OEM-spec air filters. Don't ignore minor codes; they often escalate into bigger emissions failures.