P0172 on 2022 GMC Terrain: Causes and Fixes for System Too Rich

What's Unique About the 2022-2022 Gmc TERRAIN NA

The 1.5L turbo engine in the 2022 GMC Terrain is highly susceptible to the charge air cooler (CAC) outlet pipe blowing off the throttle body. This is a well-documented issue, cited in multiple GM Technical Service Bulletins (TSBs) like 22-NA-224, which supersedes earlier versions. This massive air leak occurs after the Mass Airflow (MAF) sensor, causing the engine computer to inject fuel for air that never reaches the cylinders. The ECM misinterprets this as a rich condition and triggers P0172, often accompanied by underboost code P0299.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light (Malfunction Indicator Lamp) is on
• "Reduced Engine Power" message displayed on the dash
• Poor acceleration, hesitation, and rough running
• Rough or unstable idle
• Engine may stall at low speeds or when coming to a stop
• Strong smell of raw fuel from the exhaust
• Black smoke from the exhaust
• Noticeably poor fuel economy

Most Likely Causes

1. Charge Air Cooler (CAC) Outlet Pipe Disconnected from Throttle Body 🔴 High Probability This is a widely known failure on this platform, addressed by GM in TSBs 22-NA-224 (which supersedes PIP5651G) and recall N192271200 for prior model years. The factory retaining clip may not provide enough force to hold the pipe under turbo boost pressure, causing it to separate.
   How to confirm: Visually inspect the large air duct connecting the intercooler to the engine's throttle body. It will be visibly disconnected or loose. This is often accompanied by codes P0299, P0101, and P1101.
   Typical fix: Reconnect the pipe to the throttle body. Inspect the O-ring seal and retainer clip for damage and replace if necessary. An improved retainer clip (GM Part #13434668) was specified in recall N192271200 and should be used for a more permanent repair.
   Est. part cost: $0-$25
2. Fuel Dilution of Engine Oil 🟡 Medium Probability Direct-injection turbo engines used for frequent short trips may not get hot enough to burn off fuel that gets past the piston rings. This fuel contaminates the oil, and the PCV system draws these fuel vapors into the intake, creating a rich condition. TSB #18-NA-246 directly addresses this cause.
   How to confirm: Remove the oil filler cap or dipstick and check for a strong gasoline smell. The oil level may also be over the full mark. The presence of oil pressure codes like P06DE or P0521 alongside P0172 is another strong indicator of severe fuel dilution.
   Typical fix: Change the engine oil and filter. If the problem persists, an ECM software update and/or a revised PCV valve may be required as per TSB #18-NA-246. Advising the driver to take longer trips to ensure the engine fully warms up can also help prevent recurrence.
   Est. part cost: $40-$80
3. Leaking High-Pressure Fuel Pump (HPFP) ⚪ Low Probability The high-pressure fuel pump on GM direct-injection engines can develop internal leaks, allowing raw gasoline to seep into the crankcase and mix with the engine oil. 🎬 See how to diagnose a leaking high-pressure fuel pump GM issued Customer Satisfaction Program N182199610 for some 2019 models for a cracking HPFP.
   How to confirm: This is often suspected after an oil change temporarily resolves the P0172 code, only for it to return quickly as the new oil becomes saturated with fuel. A diagnostic method involves disconnecting the PCV hose from the intake and observing if fuel trims improve, indicating excess vapors from the crankcase.
   Typical fix: Replacement of the high-pressure fuel pump. The associated high-pressure fuel feed pipe is typically a one-time-use part and should also be replaced.
   Est. part cost: $200-$400
4. Dirty or Faulty Mass Airflow (MAF) Sensor ⚪ Low Probability While not a platform-specific weakness, a MAF sensor can become contaminated, causing it to under-report airflow and lead to a rich mixture. It's often misdiagnosed when the real issue is the CAC pipe. TSB 22-NA-224 specifically warns against replacing the MAF unless it is confirmed to be damaged.
   How to confirm: Inspect the sensor for contamination. A scan tool can monitor MAF readings to see if they are logical for the engine speed and load. At idle, a healthy 1.5L engine should read approximately 1.5-2.0 g/s.
   Typical fix: Clean the MAF sensor with a dedicated MAF sensor cleaner. If cleaning doesn't work, the sensor must be replaced.
   Est. part cost: $10-$150

Rare But Worth Checking

• Leaking Fuel Injector: A fuel injector can get stuck open, dumping excess fuel into one cylinder. This is less common than the CAC pipe issue but can cause a rich condition. This would typically be diagnosed with an injector balance test.
• Faulty Upstream Oxygen (O2) Sensor: The sensor responsible for detecting the rich condition could be faulty itself, sending incorrect data to the ECM. However, this usually triggers a specific O2 sensor code as well and should not be replaced unless tested and confirmed bad.
• Stuck Open EVAP Purge Valve: The EVAP purge solenoid can stick open, allowing unmetered fuel vapors from the charcoal canister to enter the intake manifold at idle. This creates a rich condition that a smoke test for vacuum leaks might miss. It can be tested by removing the valve and trying to blow through it; it should be closed when not powered.

Diagnosis Steps

1. Scan the ECM for all stored trouble codes. Note if P0299, P0101, P1101, or P0506 are present alongside P0172, as this combination strongly indicates a disconnected charge air cooler pipe.
2. Perform a thorough visual inspection of the engine bay, focusing on the large air intake tube that runs from the intercooler to the throttle body on the engine. Check if it has popped off the throttle body. This is the most common failure.
3. If the pipe is disconnected, inspect the pipe end, the throttle body inlet, the O-ring seal, and the retainer clip for any cracks or damage before reconnecting. TSBs note that the throttle body itself is rarely damaged.
4. If the intake system is secure, check the engine oil. Remove the oil cap or dipstick and smell for a strong odor of raw gasoline. An overfull dipstick is also a sign.
5. If the oil smells strongly of fuel, perform an engine oil and filter change. Clear the codes and drive the vehicle to see if the code returns. Advise longer driving trips to allow the engine to fully warm up.
6. If the code returns quickly after an oil change, the high-pressure fuel pump is the next likely suspect for leaking fuel internally and will likely require replacement.
7. If no fuel is in the oil and the intake is secure, inspect the air filter to ensure it is clean and properly seated.
8. With a scan tool, monitor short-term and long-term fuel trims. Consistently large negative numbers (e.g., -20% or more) confirm the ECM is trying to correct a rich condition.
9. Test the MAF sensor and upstream O2 sensor with a scan tool to ensure they are functioning correctly and providing logical data, but do not replace them unless they are confirmed faulty.

Parts You'll Likely Need

• Charge Air Cooler Outlet Pipe Retainer Clip (OEM #13434668) — This is the updated part from GM designed to prevent the charge air cooler pipe from disconnecting from the throttle body. It was specified in recall N192271200.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $15-$25
  Aftermarket price range: $10-$20
• Charge Air Cooler Outlet Pipe (OEM #849)

Related Codes That Often Appear With This One

• P0299 — Engine Underboost. This code is almost always present with P0172 when the charge air cooler pipe disconnects, as the pressurized air from the turbo escapes before it can be used. It is explicitly mentioned in TSBs and recalls for this issue.
• P0101 — Mass Air Flow (MAF) Sensor Performance. This code sets because the air measured by the MAF sensor doesn't match what the engine expects to see, a direct result of the massive air leak from the disconnected pipe.
• P1101 — Intake Air Flow System Performance. Similar to P0101, this GM-specific code indicates a discrepancy between measured and expected airflow, pointing directly to a major intake leak like the CAC pipe.
• P0506 — Idle Speed Low. The large, unmanaged air leak makes it impossible for the ECM to control idle speed correctly, often causing it to be low or unstable.
• P06DE / P0521 — Engine Oil Pressure Codes. TSBs #18-NA-246 and #22-NA-056 link these codes with P0172. Their presence strongly suggests the engine oil is severely diluted with fuel, which degrades the oil's viscosity and affects the oil pressure control system.

Technical Service Bulletins (TSBs) & Recalls

• 22-NA-224: Supersedes previous bulletins. Details the primary repair for a disconnected Charge Air Cooler (CAC) outlet tube causing P0172 and other codes.
• PIP5651G: Earlier preliminary bulletin identifying the CAC pipe disconnection as the cause.
• 18-NA-246: Addresses P0172 caused by fuel accumulation in the crankcase from frequent short-trip driving.
• N192271200: Voluntary Emissions Recall for 2019 models to install an improved CAC retainer clip (#13434668) to prevent disconnection.
• N192266090 / N182199610: Service updates and customer satisfaction programs related to the CAC pipe and high-pressure fuel pump issues on certain model years.
• 22-NA-056: Links P0172 with oil pressure codes (P06DE/P0521) when the cause is fuel-contaminated oil.

Platform-Specific Known Issues

• Owner Experience: The Classic CAC Pipe Blow-Off: A common owner story involves driving normally when the vehicle suddenly loses power, displays the 'Reduced Engine Power' message, and the Check Engine Light comes on. Upon scanning the codes, P0172 is found along with P0299 (Engine Underboost). A quick visual inspection under the hood reveals the large plastic air tube has popped completely off the throttle body. The fix is often as simple as pushing the pipe back on and re-engaging the metal clip. For a permanent solution, many owners and dealers install the updated retainer clip (Part #13434668) to prevent it from happening again.

Mechanic-Grade Diagnostic Values

• Long-Term Fuel Trim (LTFT) — expected: -10% to +10%. Failure: Consistently more negative than -10%, with the P0172 code often setting when values exceed -20% to -25%.
• Mass Air Flow (MAF) Sensor Reading at Idle — expected: Approximately 1.5 to 2.5 g/s for the 1.5L engine at warm idle. General range for similar engines is 2-7 g/s.. Failure: A reading significantly lower than expected, or readings that are stuck or do not increase smoothly with RPM.
• High-Pressure Fuel System Pressure — expected: 2,000 to 2,800 PSI under operation.. Failure: Pressure significantly outside the expected range, which may indicate a failing High-Pressure Fuel Pump (HPFP).
• Upstream O2 Sensor (Bank 1, Sensor 1) Voltage — expected: Continuously fluctuating between approximately 0.1V (lean) and 0.9V (rich) on a warm, closed-loop engine.. Failure: A sensor that is stuck high (e.g., >0.8V) or responds very slowly.

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Fuel Trim Reset — After a repair (like an oil change for fuel dilution or cleaning a MAF sensor), this function clears the learned long-term fuel trim values, forcing the ECM to relearn immediately and confirming if the fix was successful.
• GDS2 (GM Global Diagnostic System 2): Idle Learn Reset / Throttle Learn Reset — This function should be used after cleaning or replacing the throttle body to reset the learned idle and throttle position values in the ECM, preventing an erratic or incorrect idle.

Wiring & Ground Locations

• Throttle Body Connector (M75) — The 6-pin electrical connector on the electronic throttle body.. Damage to this connector or its wiring can directly cause idle control and performance faults that may accompany P0172. Key pins include Throttle Position Sensor signals (Pins 33 & 35) and Throttle Actuator Control motor pins (Pins 32 & 16).
• G112 Ground — On some similar GM models, this primary ECM ground is located on the lower left front of the engine block.. A poor connection at a primary engine or ECM ground can cause a wide range of erratic sensor readings and improper actuator control, leading to various driveability codes including P0172. While a rare cause, it's a foundational check.
• MAF Sensor Connector — On the air intake tube, immediately after the air filter housing. It is a 5-pin or 8-pin connector held by a red locking tab.. A loose or corroded connection here will cause MAF performance codes (P0101, P0102, P0103) which can accompany P0172, especially if the CAC pipe is not the cause.

"I Checked Everything" — The Actual Cause

• In cases where a smoke test reveals no vacuum leaks, an intermittently sticking EVAP purge solenoid can be the cause. The valve may test fine initially but fail intermittently, allowing unmetered fuel vapor into the intake and causing a rich condition that a smoke test would miss.
• A leaking high-pressure fuel pump (HPFP) can cause a rich condition with no external vacuum leak. Fuel leaks internally into the crankcase, contaminates the oil, and the fuel-rich vapor is then drawn into the intake via the PCV system, triggering P0172.

OEM Part Supersession History

• Unknown, original factory clip → 13434668 — The original clip design was insufficient to hold the CAC pipe to the throttle body under boost, leading to disconnection. Part 13434668 is an improved design specified in recalls and TSBs to prevent this failure.
• 13434668 → 84828210 — Standard part number supersession by GM.
  Heads up: 84828210 is the direct replacement for 13434668 and should be used if the older number is unavailable.