P026A
DTC P026A
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC P026A
- Charge Air Cooler (CAC) Low Efficiency
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The charge air cooler (CAC) temperature sensor, intake air temperature (IAT) sensor 1, and IAT sensor 2 are variable resistors. The IAT sensor 1 is part of the Mass Air Flow (MAF/IAT) sensor assembly which is located in the intake air duct after the air cleaner assembly. The IAT sensor 2 is located in the CAC inlet duct. The CAC temperature sensor is located in the CAC outlet duct before the throttle body assembly. The engine control module (ECM) supplies 5 V to the signal circuits, and a ground for each sensor's low reference circuit. The ECM monitors the CAC temperature sensor and the IAT sensor 2 circuits in order to calculate the temperature of the fuel air. The ECM monitors the CAC sensor and IAT sensor 2 signal for excessively high or low voltages, or for a voltage that is not in correlation with the other sensor's start up signal.
The ECM monitors the signals from three sensors to calculate the efficiency of the cooler:
* CAC temperature sensor
* IAT sensor 1
* IAT sensor 2
Conditions for Running the DTC
* Engine speed is greater than 600 to 850 RPM, depending on engine coolant temperature (ECT) and BARO, for at least 10 s.
* The ECT is between 70-123°C (158-253°F).
* The Ambient Air Temperature is warmer than -7°C (+19.4°F).
* The difference between the CAC Inlet Temperature and the Ambient Air Temperature is at least 40°C (72°F).
* The Intake Air Flow (IAF) Valve Position is 5 % or less.
* The MAF signal is between 83.33-152.77 g/s.
* The vehicle speed is at least 60 Km/h (37 mph).
* The BARO is greater than 75 kPa.
* The calculated fuel rate is between 20 mm(3) and 50 mm(3).
* This DTC runs once per key cycle when the above conditions exist.
Conditions for Setting the DTC
The ECM detects that the CAC efficiency, which is based on the following sensor signals, does not fall below a calibrated threshold for 60 s.
* CAC Temperature Sensor signal
* Intake IAT Sensor 2 signal
* Calculated Ambient Air Temperature value
Action Taken When the DTC Sets
DTC P026A is a Type B DTC.
Conditions for Clearing the DTC
DTC P026A is a Type B DTC.
Diagnostic Aids
* Skewed temperature sensors may cause this DTC to set.
* A grill cover may aid proper air flow.
* The CAC Temperature Sensor is located after the outlet from the CAC. The CAC Temperature Sensor is also known as the CAC Outlet Temperature Sensor.
* The IAT Sensor 2 is located before the inlet to the CAC. The IAT Sensor 2 is also known as the CAC Inlet Temperature Sensor.
* The ECM calculates the Ambient Air Temperature value from the IAT Sensor 1 signal. The IAT Sensor 1 is part of the MAF/IAT assembly located in the intake air duct after the air cleaner assembly.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
Note:
* Perform Steps 1 and 2 of this verification procedure only if the ignition has been OFF for 8 hours or more.
* The vehicle sitting in direct sun light or having the block heater ON will skew the results.
1. Ignition ON, observe the following scan tool parameters. The readings should be within 15°C (27°F) of each other.
* IAT Sensor 1 Sensor
* IAT Sensor 2 Sensor
* Start-Up ECT Sensor
* Ambient Air Temp.
2. Ignition ON, observe the following scan tool parameters. The readings should be within 35°C (63°F) of each other.
* CAC Temperature Sensor
* IAT Sensor 2
3. Engine idling, verify the appropriate scan tool parameters' readings are within the specified range. The readings depend on the current ambient temperature and the vehicle operating conditions.
* -39 to +198°C (-38 to +388°F); CAC Temperature Sensor
* -39 to +213°C (-38 to +415°F); IAT Sensor 2
* -39 to +213°C (-38 to +415°F); IAT Sensor 1
* -39 to +213°C (-38 to +415°F); Ambient Air Temp.
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
Note: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
1. Inspect for the following conditions:
* A loose or disconnected CAC hose or pipe
* A blocked or obstructed CAC, including: after market grill covers
* Any snow or ice build-up at the CAC in cold climates
* Any mud or dirt build-up at the CAC
* A restricted or collapsed air intake duct
* An intake manifold leak
* A MAP sensor seal that is leaking, missing, or damaged
• If you find any of the above conditions, repair as necessary.
2. Engine idling at operating temperature. Observe the Airflow Leak Equivalence Ratio parameter while slowly increasing the engine speed until reaching wide open throttle (WOT). After 10 s, the value should stabilize and be between 0.8:1 and 1.2:1.
• If not within the specified range, test the charge air cooler system and air inlet system for leaks. Perform the Full System Air Leak Test and the Induction System Smoke Test. Refer to Charge Air Cooler Diagnosis (Induction System Smoke Test) (Charge Air Cooler Diagnosis (Induction System Smoke Test)) Charge Air Cooler Diagnosis (Charge Air Cooler Air Leak Test) (Charge Air Cooler Diagnosis (Charge Air Cooler Air Leak Test)) Charge Air Cooler Diagnosis (Full System Air Leak Test) (Charge Air Cooler Diagnosis (Full System Air Leak Test)). If no air leaks are found, test all of the temperature sensors' circuits in the Circuit/System Verification for high resistance.
3. Ignition OFF, disconnect the harness connector at the appropriate temperature sensor as determined in the Circuit/System Verification.
4. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohm between the appropriate low reference circuit terminal 2 or B and ground.
• If greater than the specified range, test the appropriate low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.
5. Ignition ON, verify the scan tool parameter of the appropriate temperature sensor is colder than -39°C (-38°F).
• If warmer than the specified range, test the appropriate signal circuit terminal 1 or A for a short to ground. If the circuit tests normal, replace the K20 ECM.
Note: If a short to voltage is found on the sensor signal circuit, the 3A fuse in the jumper wire will open.
6. Install a 3A fused jumper wire between the appropriate signal circuit terminal 1 or A and ground. Verify the appropriate scan tool parameter is warmer than
* 197°C (387°F); Charge Air Cooler Temperature
* 213°C (415°F); IAT Sensor 1
* 213°C (415°F); IAT Sensor 2
• If colder than the specified range, test the appropriate signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
7. If all circuits test normal, test or replace the appropriate temperature sensor.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Charge Air Temperature Sensor Replacement (Turbocharger) (Charge Air Temperature Sensor Replacement (Turbocharger)) Charge Air Temperature Sensor Replacement (Outlet Pipe) (Charge Air Temperature Sensor Replacement (Outlet Pipe)) for Charge Air Cooler Temperature Sensor Replacement.
* Mass Airflow Sensor with Intake Air Temperature Sensor Replacement (Service and Repair)
* Intake Air Temperature (IAT) Sensor 2 Replacement (Intake Air Temperature (IAT) Sensor 2 Replacement)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming