P0401 on Cadillac
Exhaust Gas Recirculation Flow Insufficient
P0401 on Cadillac vehicles indicates exhaust gas recirculation flow insufficient. Au7o has documented this code across 3 Cadillac models — most commonly on CTS, CTS-V, Escalade. This code means the Exhaust Gas Recirculation (EGR) system is not flowing enough exhaust back into the engine. The EGR system recirculates a small amount of exhaust into the intake to lower combustion temperatures and reduce nitrogen oxide (NOx) emissions; the computer has determined the actual flow is below what it commanded. The most common reason is carbon buildup clogging the EGR valve or its passages. You may notice pinging/knocking, rough idle, or a check engine light, and the car will fail emissions testing. Typical repair costs on Cadillac range from $800 to $3,500, depending on the specific model and root cause.
Common Causes of P0401
- •Carbon buildup clogging the EGR valve or passages
- •Stuck or faulty EGR valve
- •Blocked or restricted EGR ports/tubes
- •Faulty EGR temperature or position sensor
- •Faulty DPFE/EGR pressure sensor (on applicable systems)
- •Vacuum leak or failed vacuum control (vacuum-operated EGR)
- •Wiring or connector problems at the EGR valve
P0401 on Cadillac by Model
Cadillac CTS(1 issue)
- Electric Power Steering Rack Failure2008-2013
The 2nd generation CTS (2008-2013) uses an electric power steering rack that can fail, causing heavy or intermittent steering assist. The electric motor integrated into the steering rack wears out, or the steering control module loses communication. Symptoms include sudden loss of power steering assist (steering becomes very heavy), intermittent assist that cuts in and out, and steering warning lights. The entire rack assembly must be replaced as the motor is not serviceable separately.
Cadillac CTS-V(1 issue)
- Magnetic Ride Control Shock Failure2009-2019
The CTS-V (2nd and 3rd gen) comes standard with Magnetic Ride Control (MRC) shocks that use magnetorheological fluid to adjust damping. These expensive shocks have a limited lifespan, typically 60,000-100,000 miles, after which the MR fluid degrades and the shocks either become too stiff, too soft, or leak. Replacement with OEM MRC shocks is very expensive ($500-800 per shock). Many owners switch to traditional high-performance shocks to avoid the recurring cost.
Cadillac Escalade(1 issue)
- Air Suspension / Magnetic Ride Control Compressor Failure2007-2020
The Cadillac Escalade with Autoride (air suspension) or Magnetic Ride Control uses an air compressor and electronic shocks that commonly fail between 80,000-120,000 miles. The air compressor burns out from continuous cycling caused by slow air leaks in the air springs (bags). Failed air springs cause the vehicle to sag at one or more corners, and the compressor overworks trying to compensate. The Magnetic Ride Control shocks contain magnetorheological fluid that degrades over time, causing a harsh or bouncy ride. Common on 2007-2014 (3rd gen) and 2015-2020 (4th gen) Escalades equipped with these options.
Looking for P0401 on a different make?
View P0401 across all makes →Frequently Asked Questions
What does P0401 mean on Cadillac?▼
P0401 stands for "Exhaust Gas Recirculation Flow Insufficient." This code means the Exhaust Gas Recirculation (EGR) system is not flowing enough exhaust back into the engine. The EGR system recirculates a small amount of exhaust into the intake to lower combustion temperatures and reduce nitrogen oxide (NOx) emissions; the computer has determined the actual flow is below what it commanded. The most common reason is carbon buildup clogging the EGR valve or its passages. You may notice pinging/knocking, rough idle, or a check engine light, and the car will fail emissions testing. On Cadillac specifically, this code is documented across 3 models.
What causes P0401 on Cadillac vehicles?▼
Common causes on Cadillac: Carbon buildup clogging the EGR valve or passages, Stuck or faulty EGR valve, Blocked or restricted EGR ports/tubes, Faulty EGR temperature or position sensor, Faulty DPFE/EGR pressure sensor (on applicable systems). Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0401 on a Cadillac?▼
Repair costs on Cadillac range from $800 to $3,500, depending on the specific model and root cause.
Which Cadillac models have P0401 documented?▼
Au7o has documented P0401 on 3 Cadillac models: CTS, CTS-V, Escalade.