Cracked or disconnected EGR supply tube between the exhaust manifold and the EGR valve; Loose or missing EGR tube mounting bolts or fittings; Failed gasket at the EGR valve inlet or exhaust manifold connection; Corroded or rusted-through EGR supply pipe, especially on older GM vehicles; Leaking differential pressure feedback EGR sensor or its hose connections; Damaged or misrouted EGR valve vacuum supply line allowing false air; Rarely, a stuck-open EGR valve that creates a reverse flow condition

DTC codes / GM codes / P1407

P1407 · GMEGR Air Intrusion In Exhaust Supply To EGR Valve

Q: What does code P1407 mean?

EGR Air Intrusion In Exhaust Supply To EGR Valve. P1407 on a GM vehicle indicates that the engine computer has detected an unexpected air intrusion in the exhaust supply path to the exhaust gas recirculation (EGR) valve. The powertrain control module (PCM) uses the EGR system's differential pressure feedback sensor to compare expected exhaust backpressure with actual readings, and it sets this code when the signal suggests outside air is entering the tube that feeds exhaust to the EGR valve.

P1407 on a GM vehicle indicates that the engine computer has detected an unexpected air intrusion in the exhaust supply path to the exhaust gas recirculation (EGR) valve. The powertrain control module (PCM) uses the EGR system's differential pressure feedback sensor to compare expected exhaust backpressure with actual readings, and it sets this code when the signal suggests outside air is entering the tube that feeds exhaust to the EGR valve.

SystemPowertrain

Code typeGM specific

SeverityMedium

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rough idle or idle surge when the engine is cold or at operating temperature
Slight hesitation or stumble during light acceleration
Poor fuel economy in some cases due to incorrect EGR flow
Intermittent engine ping or knock under load if the air intrusion leans the mixture
Failed emissions test due to elevated oxides of nitrogen (NOx)

Common causes, most likely first

Cracked or disconnected EGR supply tube between the exhaust manifold and the EGR valve
Loose or missing EGR tube mounting bolts or fittings
Failed gasket at the EGR valve inlet or exhaust manifold connection
Corroded or rusted-through EGR supply pipe, especially on older GM vehicles
Leaking differential pressure feedback EGR sensor or its hose connections
Damaged or misrouted EGR valve vacuum supply line allowing false air
Rarely, a stuck-open EGR valve that creates a reverse flow condition

How to diagnose and fix it

Inspect the entire EGR supply tube for cracks, rust holes, and loose connections, and repair or replace as needed
Check and replace the EGR tube gaskets at both the exhaust manifold and EGR valve ends
Verify that the differential pressure feedback EGR sensor hoses are secure and free of cracks, and replace the sensor if it is leaking internally
Use a scan tool to monitor EGR pressure sensor readings while wiggling the supply tube to confirm an intermittent leak
Perform a smoke test on the EGR supply system to pinpoint air intrusion points
Clear the code and test-drive the vehicle through the EGR monitor's enable criteria to confirm the repair
If the code returns, check for exhaust manifold cracks or warping that could allow air into the EGR passage

Hidden Causes of P1407 Air Intrusion

A loose oil dipstick or missing oil filler cap can sometimes be misdiagnosed as an EGR air intrusion because crankcase vapors affect the pressure sensor readings, so always check those first.
The differential pressure feedback EGR sensor itself can develop an internal leak that mimics a cracked supply tube, and replacing the tube without testing the sensor often leads to a repeat code.
On some GM engines, a warped exhaust manifold or a failed manifold gasket allows outside air to be drawn into the EGR passage, setting P1407 even though the EGR tube looks perfect.
Aftermarket EGR tubes with poor-quality welds or incorrect bends are a common source of repeat P1407 codes, so insist on OEM-quality replacement parts.
This code does not always mean the EGR valve is faulty; replacing the valve without diagnosing the supply tube and sensor is a frequent and expensive misdiagnosis.

Can I keep driving with P1407?

You can usually continue driving with P1407, but avoid heavy acceleration and long trips until the leak is repaired because the engine may run lean under load and emissions will be elevated. If you notice rough running or knocking, have it checked promptly.

Tools that help

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Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.