What does it mean?
This generic powertrain/engine diagnostic code generally applies to diesel engines built after 2004, including but not limited to certain Ford, Dodge, GM, Mercedes, Mitsubishi, Nissan, Suzuki, and VW vehicles.
This valve is located between the intake manifold and the air filter, similar to a throttle body. It is used to create a small vacuum that will draw exhaust gases into the intake manifold.
The Powertrain Control Module (PCM) tells the Exhaust Gas Recirculation (EGR) throttle control valve where to position itself. This code examines the voltage signals from the EGR throttle control valve to determine if they are correct based on PCM inputs. This code may have been set due to mechanical or electrical issues.
Troubleshooting steps may vary depending on the manufacturer, the type of EGR throttle control valve, and the wire colors.
Symptoms of a P0488 engine code may include:
- Malfunction Indicator Lamp (MIL) illuminated
- Active post-treatment regeneration time longer than normal (it will take more time for the exhaust system to heat up and burn off soot accumulated inside the diesel particulate filter/catalytic converter)
Possible causes for this code being set are:
- Open in the signal circuit between the EGR throttle control valve and the PCM
- Short to voltage in the signal circuit to the EGR throttle control valve
- Short to ground in the signal circuit to the EGR throttle control valve
- Faulty EGR throttle control valve – internally shorted
- Failed PCM – unlikely
Diagnostic and Repair Procedures
A good starting point is always to check the Technical Service Bulletins (TSBs) for your specific vehicle. Your issue may be a known problem with a known fix released by the manufacturer and could save you time and money during diagnosis.
Next, locate the EGR throttle control valve on your specific vehicle. This valve is located between the intake manifold and the air filter, similar to a throttle body. Once located, visually inspect the connectors and wiring. Look for scratches, rubbing, exposed wires, burns, or melted plastic. Disconnect the connectors and carefully inspect the terminals (the metal parts) inside the connectors. Check if they appear burnt or have a greenish tint indicating corrosion. Use electrical contact cleaner and a plastic-bristled brush if terminal cleaning is necessary. Allow it to dry and apply dielectric silicone grease where the terminals make contact.
Scan Tool
If you have a scan tool, clear the diagnostic codes from the memory and see if this code returns. If it does not, the connections were likely your problem.
If the P0488 code returns, we will need to test the EGR throttle control valve and its associated circuits. Typically, there are 3 or 4 wires going to the EGR throttle control valve. Disconnect the harness going to the EGR throttle control valve. With a digital voltmeter (DVOM), test the signal circuit of the EGR throttle control valve (red lead to the valve’s signal circuit, black lead to a good ground). If there is no 5 volts at the valve, or if you see 12 volts at the valve, repair the wiring from the PCM to the valve, or possibly a faulty PCM.
If that checks out, ensure there is a good ground at the EGR throttle control valve. Connect a test light to the positive 12V battery terminal (red terminal) and touch the other end of the test light to the ground circuit going to the EGR throttle control valve circuit ground. If the test light does not illuminate, this would indicate a circuit problem. If it lights up, wiggle the wiring harness going to the EGR throttle control valve to see if the test light flickers, indicating an intermittent connection.
Conclusion
If all previous tests have passed and you continue to get a P0488, this would most likely indicate a faulty EGR throttle control valve, although a failed PCM cannot be ruled out until the EGR throttle control valve has been replaced.