Encountering an OBD2 code P1390 on your 1996 Mitsubishi Eclipse can be concerning, especially after recent engine work. This article delves into the specifics of the P1390 code, tailored for your vehicle, and provides a troubleshooting approach to resolve it effectively. It’s important to understand that while generic OBD2 codes offer a starting point, their specific meaning can vary between manufacturers. Let’s clarify what P1390 signifies for your Mitsubishi Eclipse and how to diagnose and fix the issue.
For a 1996 Mitsubishi Eclipse, the OBD2 code P1390 typically points to a problem within the Camshaft Position Sensor (CMP) circuit or related timing issues. It’s crucial to differentiate this from interpretations that might associate P1390 with “Timing Belt Skipped One Or More Teeth” in other vehicle brands like Dodge, or “Wheel Speed Sensor” as seen in some generic OBD2 code lists. For your Mitsubishi Eclipse, focus on the camshaft position sensor and its role in engine timing.
The Camshaft Position Sensor is vital for your engine’s operation. It monitors the camshaft’s position and sends this information to the Engine Control Module (ECM). This data is essential for proper ignition timing and fuel injection sequencing. When the ECM detects an anomaly in the CMP sensor circuit or the camshaft timing, it can trigger the P1390 code.
Several factors can lead to a P1390 code in your 1996 Mitsubishi Eclipse:
- Camshaft Position Sensor Failure: The sensor itself might be faulty due to wear, damage, or electrical issues.
- Wiring and Connection Problems: Issues within the CMP sensor circuit, such as frayed wires, loose connectors, corrosion, or shorts, can disrupt the signal to the ECM.
- Timing Belt Misalignment: While you were careful during the timing belt replacement, even a slight misalignment can cause timing discrepancies that the CMP sensor might detect, leading to the P1390 code. This is especially relevant after a water pump seizure and valve bending incident, as these events can sometimes subtly affect engine timing even after repair.
- ECM Issues: In rare cases, a malfunctioning ECM could misinterpret signals or falsely trigger the P1390 code. However, this is less likely than sensor or wiring problems.
- Resurfaced Cylinder Head: The concern raised about resurfacing the cylinder head (8 mil removed) potentially affecting valve timing is less likely to directly cause a P1390 code related to the CMP sensor on a 1996 Mitsubishi Eclipse. While significant material removal could theoretically alter timing slightly, the CMP sensor typically compensates for minor variations. It’s more probable that any timing issue arose from the timing belt installation process itself.
Diagnosing and Troubleshooting P1390:
-
Visual Inspection: Begin with a thorough visual inspection. Check the CMP sensor wiring and connectors for any obvious damage, looseness, or corrosion. Ensure the sensor is securely mounted.
-
Timing Mark Verification: Re-verify your timing belt installation. Although you checked the cam sprocket timing mark through the inspection hole, double-checking the crankshaft and camshaft alignment marks according to the 1996 Mitsubishi Eclipse service manual is crucial. Using a dowel to find TDC is a good starting point, but confirm the alignment with the specific timing marks on your engine. The rib on the timing cover might be a visual aid, but always refer to the official service manual for precise timing mark locations.
Alt text: Timing marks on a 1996 Mitsubishi Eclipse engine for verifying camshaft and crankshaft alignment during timing belt installation.
-
Sensor Testing: Use a multimeter to test the Camshaft Position Sensor. Consult the service manual for your 1996 Mitsubishi Eclipse for the specific testing procedure and expected resistance or voltage values. This will help determine if the sensor is functioning correctly.
-
Wiring Circuit Test: Inspect the wiring harness leading to the CMP sensor. Use a multimeter to check for continuity, shorts to ground, and shorts to voltage in the wiring. Repair any wiring issues found.
-
Scan Tool Data: Utilize an OBD2 scan tool to read live data from the CMP sensor. Observe the sensor readings while the engine is running. Erratic or absent signals can indicate a faulty sensor or wiring problem. Some advanced scan tools might offer specific CMP sensor tests.
-
Consider a “Relearn” Procedure (If Applicable): While a dedicated “relearn timing” procedure might not be explicitly required for a CMP sensor replacement on a 1996 Mitsubishi Eclipse in the same way it is for some throttle position sensors, clearing the P1390 code with a scan tool after addressing the likely cause is essential. This allows the ECM to reset and reassess the sensor signals. If the code returns after clearing, it indicates a persistent issue.
Addressing Potential Causes:
- If the CMP sensor is faulty: Replace it with a new sensor. Ensure you use a sensor compatible with your 1996 Mitsubishi Eclipse.
- If wiring issues are found: Repair or replace the damaged wiring or connectors. Ensure secure and clean connections.
- If timing belt misalignment is suspected: Carefully remove the timing covers and re-verify the timing marks. If misaligned, correct the timing belt installation according to the service manual procedures.
- If ECM issues are suspected (least likely): ECM problems are complex to diagnose without specialized equipment. Rule out all other possibilities first. If you suspect an ECM issue after thorough troubleshooting, consult a professional mechanic with experience in Mitsubishi vehicles.
Conclusion:
OBD2 code P1390 on your 1996 Mitsubishi Eclipse most likely indicates a problem with the Camshaft Position Sensor circuit or engine timing. By systematically diagnosing the sensor, wiring, and timing belt alignment, you can effectively pinpoint the root cause. Remember to prioritize accurate timing belt installation and proper sensor function for optimal engine performance. If you are unsure about any of these steps, seeking assistance from a qualified mechanic experienced with Mitsubishi vehicles is always a prudent decision.
