DTC Code P066E: Diagnosis and Solutions
What is Code P066E?
The generic powertrain diagnostic trouble code (DTC) P066E applies to many OBD-II vehicles, including (but not limited to) those from VW, Porsche, Ford, Toyota, GM, Chevrolet, Jeep, Chrysler, Dodge, and Ram.
When a P066E code is stored, it means that the Powertrain Control Module (PCM) has detected a low voltage condition for the glow plug control circuit of cylinder #3.
Role of Glow Plugs
Diesel engines use high compression to initiate piston movement. Since no spark is involved, the cylinder temperature must be increased to maximize compression.
Each cylinder has a glow plug screwed into the cylinder head. Battery voltage is applied to these plugs via a glow plug module or timer. When voltage is correctly applied, the plug glows red and increases the cylinder temperature.
If the PCM detects a lower voltage than expected for the glow plug of cylinder #3, the P066E code is stored, and a Malfunction Indicator Lamp (MIL) may illuminate.
Severity of Code P066E
Any code related to glow plugs can lead to driving issues. It is recommended to address a P066E promptly.
Symptoms of a P066E Code
- Excessive black smoke from the exhaust
- Engine running problems
- Delayed engine starting
- Reduced fuel efficiency
- Recording of engine misfire codes
Possible Causes of Code P066E
- Faulty glow plug(s)
- Open or shorted glow plug control circuit
- Loose or faulty glow plug connector
- Defective glow plug timer
Diagnostic and Repair Procedure
1. Preparation
- Diagnostic scanner
- Reliable source of vehicle information
- Digital volt/ohmmeter (DVOM)
- Electrical diagrams and connector views
2. Visual Inspection
- Check glow plug wiring and connectors
- Inspect related fuses and relays
3. Code Analysis
- Connect the diagnostic scanner and record all codes and freeze frame data
- Clear the codes and test the vehicle to see if the P066E code returns
4. Glow Plug Testing
- Remove the glow plug and apply battery voltage
- If it glows red, it is working. Otherwise, measure its resistance and compare to manufacturer specifications
5. Control Circuit Testing
- Activate the glow plug timer with the scanner
- Measure voltage at the timer input and output
- If no voltage is present, test the power supply to the timer or PCM
6. Circuit Verification
- If voltage is detected at the PCM or timer, look for an open or shorted circuit
- Replace the circuit if necessary
Additional Tips
- A P066E can be caused by a faulty glow plug, even though it is a control circuit code
- Ensure diagnosing the correct cylinder to avoid wasting time
By following these steps, it is possible to identify and correct the cause of the P066E code to ensure optimal engine operation.