P0402 on Cadillac
Exhaust Gas Recirculation Flow Excessive
P0402 on Cadillac vehicles indicates exhaust gas recirculation flow excessive. Au7o has documented this code across 3 Cadillac models — most commonly on CTS, CTS-V, Escalade. P0402 means the Exhaust Gas Recirculation (EGR) system is flowing too much exhaust back into the intake. The EGR system intentionally routes a small amount of inert exhaust gas into the engine to lower combustion temperatures and reduce nitrogen-oxide emissions, but the flow must be metered precisely. When the PCM determines the flow is excessive — often because the EGR valve is stuck open or letting gas through when it shouldn't — it sets this code. Too much EGR can cause rough idle, stalling, hesitation, and a check engine light. Typical repair costs on Cadillac range from $800 to $3,500, depending on the specific model and root cause.
Common Causes of P0402
- •EGR valve stuck open or not closing fully
- •Failed or sticking EGR valve diaphragm/solenoid
- •Carbon buildup holding the EGR valve open
- •Faulty EGR position or differential pressure (DPFE) sensor
- •Leaking EGR valve gasket or pintle seat
- •Vacuum control or solenoid fault commanding EGR open
- •Wiring or connector problems in the EGR control circuit
P0402 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 P0402 on a different make?
View P0402 across all makes →Frequently Asked Questions
What does P0402 mean on Cadillac?▼
P0402 stands for "Exhaust Gas Recirculation Flow Excessive." P0402 means the Exhaust Gas Recirculation (EGR) system is flowing too much exhaust back into the intake. The EGR system intentionally routes a small amount of inert exhaust gas into the engine to lower combustion temperatures and reduce nitrogen-oxide emissions, but the flow must be metered precisely. When the PCM determines the flow is excessive — often because the EGR valve is stuck open or letting gas through when it shouldn't — it sets this code. Too much EGR can cause rough idle, stalling, hesitation, and a check engine light. On Cadillac specifically, this code is documented across 3 models.
What causes P0402 on Cadillac vehicles?▼
Common causes on Cadillac: EGR valve stuck open or not closing fully, Failed or sticking EGR valve diaphragm/solenoid, Carbon buildup holding the EGR valve open, Faulty EGR position or differential pressure (DPFE) sensor, Leaking EGR valve gasket or pintle seat. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0402 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 P0402 documented?▼
Au7o has documented P0402 on 3 Cadillac models: CTS, CTS-V, Escalade.