Technical Description of OBD-II Trouble Code
The system for controlling the intake air flow in diesel engines detects low air flow.
What does that mean?
This diagnostic trouble code (DTC) is a generic code that can apply to all diesel engines equipped with OBD-II. However, it is more commonly found in certain Chevy, Dodge, Ford, and GMC trucks.
Although it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
The Diesel Intake Air Flow Control System (DIAFCS) is typically attached to the intake manifold in the intake air stream. This system controls the amount of incoming airflow by adjusting a signal to a motor operated by the Powertrain Control Module (PCM). The motor opens and closes a throttle plate to regulate the airflow.
The PCM determines the amount of clean, filtered air entering the engine based on the Diesel Intake Airflow Position Sensor, also known as a MAF sensor. When the air flow control system is activated, the PCM should detect a change in airflow. If there is no change, it may indicate a problem with the DIAFCS system or the MAF sensor. These trouble codes are set when this input does not match the normal engine operating conditions stored in the PCM’s memory, even for a brief moment.
The PCM also checks the voltage signal from the DIAFCS to ensure it is correct when the key is initially turned on.
The code P02ED is set when a low air flow condition is detected in the diesel intake air flow control system. This could be caused by mechanical issues (such as physical damage to the control system resulting in an electrical fault) or electrical issues (such as problems with the DIAFCS motor circuit). These possibilities should not be overlooked during the troubleshooting process, especially when dealing with an intermittent problem.
The troubleshooting steps may vary depending on the manufacturer, type of DIAFCS motor/control, and wire colors.
What is the severity of this DTC?
In all cases, the severity is considered not severe. If the cause is mechanical, the typical failure is low idle speed. If it is an electrical failure, the PCM can compensate adequately.
What are some of the symptoms of the code?
Symptoms of a P02ED trouble code may include:
What are some of the common causes of the code?
Possible causes for this P02ED code may include:
What are some P02ED troubleshooting steps?
A good starting point is always to check for technical service bulletins (TSB) for your vehicle. Your issue may be a known issue with a known fix provided by the manufacturer, which can save you time and money during diagnosis.
Next, locate the DIAFCS motor/control system on your vehicle. This motor/control is usually attached to the intake manifold in the intake air stream. Once located, visually inspect the connector and wiring for any signs of damage or wear. Look for scraping, rubbing, bare wires, burn spots, or melted plastic. Disconnect the connector and carefully examine the terminals inside for any signs of burning or corrosion. If needed, clean the terminals using electrical contact cleaner and a plastic bristle brush. After cleaning, apply electrical grease to the terminals.
If a mechanical code was set, use intake cleaner and a clean rag to remove carbon deposits behind the throttle plate of the motor control system. Spray the cleaner onto the rag and wipe away the deposits. Never spray these deposits into the engine, as it can cause poor running, misfires, and potential damage to the catalytic converter and engine.
If you have a scan tool, clear the diagnostic trouble codes from memory and check if the P02ED code returns. If it does not, then the issue was most likely related to the connections.
If the P02ED code does return, further testing of the DIAFCS and its associated circuits will be necessary. With the key off, disconnect the electrical connector at the DIAFCS motor/control. Use a Digital Voltmeter to check the voltage between the ground terminal and the motor terminal at the DIAFCS sensor wiring harness connector. With the key on and the engine off, the voltmeter should read 12 volts according to the manufacturer’s specifications. If not, repair the power or ground wire, or replace the PCM. If unsure, refer to the manufacturer’s specifications for complete test procedures specific to your vehicle.
If the previous test passed and the P02ED code continues to appear, it is likely that the DIAFCS motor/control has failed. However, a failed PCM cannot be ruled out until the DIAFCS motor/control has been replaced. If unsure, seek assistance from a trained automotive diagnostician. PCMs must be programmed or calibrated to the vehicle for proper installation.
