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 engine control module (ECM) monitors three sensors' signals to calculate the efficiency of the charge air cooler (CAC):
* Intake air temperature (IAT) sensor 2
* IAT sensor 3
* CAC temperature sensor
The CAC temperature sensor, the IAT sensor 3, and the IAT sensor 2 are variable resistors. The 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 signals to calculate the temperature of the fuel air. The ECM monitors the CAC sensor and IAT sensor 3 signals for excessively high or low voltages, or for voltage that is not in correlation with the other sensor's start up signal.
The sensors are listed in direction of the intake air flow, below:
* The IAT sensor 2 is part of the Mass Air Flow (MAF/IAT) sensor assembly, located in the air cleaner assembly cover. Its signal is used by the ECM to calculate Ambient Temperature.
* The IAT sensor 3 is located in the outlet duct from the turbocharger. Its signal is used by the ECM to measure the temperature of the intake air going to the CAC inlet.
* The CAC temperature sensor is located in the CAC outlet duct before the throttle body assembly. Its signal is used by the ECM to measure the temperature of the intake air leaving the CAC.
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 mm3 and 50 mm3.
* This DTC runs once per key cycle when the above conditions exist.
Conditions for Setting the DTC
The ECM detects that the CAC efficiency does not fall below a calibrated threshold for 60 s. The CAC efficiency is based on the following sensor signals.
* CAC Temperature Sensor signal
* Intake IAT Sensor 3 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
* The IAT Sensor 3 is located before the inlet to the CAC. The IAT Sensor 3 is also known as the CAC Inlet Temperature Sensor (Turbocharger).
* 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 (Charge Air Outlet Duct).
* Skewed temperature sensors may cause this DTC to set.
* A grill cover may aid proper air flow.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
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 Control Module References for scan tool information
Circuit/System Verification
Note:
* To minimize the effects of residual engine heat and sensor internal heating elements, 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
2. Verify the following scan tool parameters are within 15°C (27°F) of each other.
* Ambient Air Temp.
* IAT Sensor 3 Sensor
* CAC Temperature Sensor
• If not within 15°C (27°F)
Refer to Circuit System Testing.
• If within 15°C (27°F)
3. Engine idling.
4. Verify the following scan tool parameters are within the specified ranges.
* Ambient Air Temp.; -38 to +148°C (-36 to +298°F)
* IAT Sensor 3; -39 to +213°C (-38 to +415°F)
* CAC Temperature Sensor;-39 to +198°C (-38 to +388°F)
• If not within the specified ranges
Refer to Circuit System Testing.
• If within the specified ranges
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
6. Verify a DTC does not set.
• If the DTC sets
Refer to Circuit/System Testing.
• If the DTC does not set
7. All OK.
Circuit/System Testing
Note: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
1. Verify none of the following conditions exist:
* A loose or disconnected charge air cooler hose or pipe
* A blocked or obstructed charge air cooler, including: after-market grill covers
* Any snow or ice build-up at the charge air cooler in cold climates
* Any mud or dirt build-up at the charge air cooler
* A restricted or collapsed air intake duct
* An intake manifold leak
* A MAP sensor seal that is leaking, missing, or damaged
* A restricted or collapsed air intake duct
* A misaligned or damaged air intake duct
* Any water intrusion in the induction system
* An Intake Manifold Resonator with a leaking seal, or a cracked or broken housing
• If a condition exists
Repair or replace the component as appropriate.
• If no condition exists
2. Engine idling at operating temperature.
1. Command the EGR solenoid to 0 % with a scan tool.
2. Observe the Airflow Leak Equivalence Ratio parameter for 10 s. Verify the parameter is between 0.8:1 and 1.2:1.
3. 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.
3. Slowly increase the engine speed until reaching wide open throttle (WOT).
4. Verify the Airflow Leak Equivalence Ratio parameter stabilizes after 10 s, between 0.8:1 and 1.2:1.
• If not stable after 10 s and between 0.8:1 and 1.2:1.
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 (Full System Air Leak Test) Charge Air Cooler Diagnosis (Full System Air Leak Test)Charge Air Cooler Diagnosis (Induction System Smoke Test) Charge Air Cooler Diagnosis (Induction System Smoke Test)
• If stable after 10 s and between 0.8:1 and 1.2:1.
5. Ignition OFF, disconnect the harness connector at the (5 Pin) B75B Mass Air Flow/Intake Air Temperature sensor (IAT sensor 2).
6. 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 2 ohms between the Intake Air Temperature sensor 2 low reference circuit terminal B and ground.
• If 2 ohms or greater
1. Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module.
2. Test for less than 2 ohms in the low reference circuit end to end.
• If 2 ohms or greater, repair the open or high resistance in the circuit.
• If less than 2 ohms replace the K20 Engine Control Module.
• If less than 2 ohms
7. Ignition ON, test for 4.8-5.2 V between the intake air temperature sensor 2 signal circuit terminal A and ground.
• If less than 4.8 V
1. Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the signal circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K20 Engine Control Module.
• If greater than 5.2 V
Note: If the signal circuit is shorted to a voltage the engine control module or the sensor may be damaged.
1. Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K20 Engine Control Module.
• If between 4.8-5.2 V
8. Ignition OFF, disconnect the harness connector at the Intake Air Temperature sensor 3.
9. 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 2 ohms between the Intake Air Temperature sensor 3 low reference circuit terminal 2 and ground.
• If 2 ohms or greater
1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module.
2. Test for less than 2 ohms in the low reference circuit end to end.
• If 2 ohms or greater, repair the open or high resistance in the circuit.
• If less than 2 ohms replace the K20 Engine Control Module.
• If less than 2 ohms
10. Ignition ON, test for 4.8-5.2 V between the intake air temperature sensor 3 signal circuit terminal B and ground.
• If less than 4.8 V
1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the signal circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K20 Engine Control Module.
• If greater than 5.2 V
Note: If the signal circuit is shorted to a voltage the engine control module or the sensor may be damaged.
1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K20 Engine Control Module.
• If between 4.8-5.2 V
11. Ignition OFF, disconnect the harness connector at the B193A Charge Air Cooler Temperature sensor.
12. 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 2 ohms between the B193A Charge Air Cooler Temperature sensor low reference circuit terminal 2 and ground.
• If 2 ohms or greater
1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module.
2. Test for less than 2 ohms in the low reference circuit end to end.
• If 2 ohms or greater, repair the open or high resistance in the circuit.
• If less than 2 ohms replace the K20 Engine Control Module.
• If less than 2 ohms
13. Ignition ON, test for 4.8-5.2 V between the B193A Charge Air Cooler Temperature sensor signal circuit terminal B and ground.
• If less than 4.8 V
1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the signal circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 ohms in the signal circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K20 Engine Control Module.
• If greater than 5.2 V
Note: If the signal circuit is shorted to a voltage the engine control module or the sensor may be damaged.
1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K20 Engine Control Module.
• If between 4.8-5.2 V
14. Test or replace the appropriate temperature sensor.
Component Testing
* Test the appropriate temperature sensor by varying the sensor temperature while monitoring the temperature with a thermometer. Compare the readings with the appropriate scan tool parameter. The values should be within 5%.
• If not within the specified range, replace the appropriate 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) (Turbocharger) for Intake Air Temperature Sensor 3; Charge Air Cooler Inlet Temperature Sensor Replacement.
* 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) (Charge Air Outlet Duct) for Charge Air Cooler Temperature Sensor; Charge Air Cooler Outlet Temperature Sensor Replacement
* Mass Airflow Sensor with Intake Air Temperature Sensor Replacement (5 Pin) Mass Airflow Sensor with Intake Air Temperature Sensor Replacement (5 Pin)Mass Airflow Sensor with Intake Air Temperature Sensor Replacement (8 Pin) Mass Airflow Sensor with Intake Air Temperature Sensor Replacement (8 Pin) for (5 Pin) Mass Air Flow/Intake Air Temperature sensor (IAT sensor 2) replacement
* Perform the scan tool Diesel Particulate Filter (DPF) Regeneration Enable Diesel Particulate Filter (DPF) Regeneration Enable procedure if the scan tool DPF Soot Mass is less than 30 g. If the scan tool DPF Soot Mass is greater than 30 g, perform the Diesel Particulate Filter (DPF) Service Regeneration Diesel Particulate Filter (DPF) Service Regeneration.
* Control Module References Control Module References for ECM replacement, programming, and setup