P0402 on GMC
Exhaust Gas Recirculation Flow Excessive
P0402 on GMC vehicles indicates exhaust gas recirculation flow excessive. Au7o has documented this code across 5 GMC models — most commonly on Acadia, Canyon, Sierra 2500HD. 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 GMC range from $150 to $4,500, 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 GMC by Model
GMC Acadia(1 issue)
- 9T65 9-Speed Transmission Harsh Shifts and Hesitation2017-2025
The second-generation Acadia (2017+) uses the GM 9T65 9-speed automatic transmission which shares known issues with the Chevrolet Traverse and Blazer. Common complaints include harsh 1-2 upshifts, hesitation between 5-15 mph, lurching on light throttle in stop-and-go traffic, and the transmission hunting between gears on hills. GM has released multiple TCM calibration updates. The transmission is extremely sensitive to fluid condition — extended intervals with aging Dexron HP fluid contribute significantly to shift quality degradation.
GMC Canyon(1 issue)
- 8L45 8-Speed Transmission Torque Converter Shudder2015-2025
The 2015+ Canyon with the 3.6L V6 uses the GM 8L45 8-speed automatic (smaller sibling of the 8L90 in full-size trucks) which suffers the same torque converter lock-up clutch shudder at light throttle between 25-50 mph. The clutch friction material degrades and contaminates the fluid. GM issued TSB 18-NA-355 and Customer Satisfaction Program 18302 extending coverage to 6 years/100,000 miles. The fix and fluid are identical to the Sierra 1500 8L90 procedure — Mobil 1 Synthetic LV ATF HP (GM 19417577). This is the same issue affecting the Chevrolet Colorado V6.
GMC Sierra 2500HD(1 issue)
- Front Axle Disconnect Actuator and IWE Hub Failure (4WD Engagement Issues)2011-2023
Sierra 2500HD 4WD trucks use a front axle disconnect system with an electronic actuator and Integrated Wheel End (IWE) hubs. The actuator motor and position sensor commonly fail between 80,000-120,000 miles, causing the 4WD system to not engage, to partially engage (binding and vibration), or to throw a 4WD Service warning. Heavy-duty truck use — particularly towing and off-road — accelerates actuator wear. The IWE hubs (vacuum-operated on some variants, electric on others) also fail, causing a grinding or clicking noise from the front axle in 2WD mode when the hub disengages incompletely.
GMC Terrain(1 issue)
- 6T40/6T45 6-Speed Transmission Shudder and Harsh Shifts2010-2017
The 2010-2017 Terrain uses the GM 6T40 (2.4L) and 6T45 (V6) 6-speed automatic transmissions, both of which suffer from torque converter shudder, harsh shifts, and solenoid failures. The shudder occurs at light throttle between 30-50 mph when the torque converter clutch locks up. Solenoid pack wear causes P0756, P0751, and P0776 transmission fault codes. The transmission is sensitive to fluid condition — the 6T40/6T45 was originally filled with Dexron VI, but older Dexron VI degrades faster than newer formulations.
GMC Yukon(1 issue)
- 8L90 8-Speed Torque Converter Shudder2015-2020
The 8L90 8-speed automatic transmission in 2015-2020 Yukon and Yukon XL suffers from widespread torque converter lock-up clutch shudder at light throttle between 25-50 mph. The clutch friction material degrades and contaminates the transmission fluid, causing the shudder to worsen over time. GM extended warranty coverage to 6 years/100,000 miles under Customer Satisfaction Program 18302. The fluid fix (Mobil 1 Synthetic LV ATF HP, GM 19417577) resolves early-stage cases; advanced cases require torque converter replacement. This is the same issue affecting all K2XX platform full-size GM SUVs and trucks.
Looking for P0402 on a different make?
View P0402 across all makes →Frequently Asked Questions
What does P0402 mean on GMC?▼
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 GMC specifically, this code is documented across 5 models.
What causes P0402 on GMC vehicles?▼
Common causes on GMC: 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 GMC?▼
Repair costs on GMC range from $150 to $4,500, depending on the specific model and root cause.
Which GMC models have P0402 documented?▼
Au7o has documented P0402 on 5 GMC models: Acadia, Canyon, Sierra 2500HD, Terrain, Yukon.