Encountering an OBD2 code can be frustrating, especially after performing engine work. If you’re facing the P1390 code after a timing belt replacement, you’re in the right place. This article will delve into the specifics of the Auto Obd2 Code P1390, helping you understand its meaning, potential causes, and how to approach diagnosis and repair.
Understanding OBD2 Code P1390
The OBD2 code P1390 can sometimes be ambiguous, as different manufacturers may use it to signify different issues. Online resources might list P1390 as “Wheel Speed Sensor 1 – G – Sensor Circuit,” which can be misleading, particularly for makes like Dodge. For Dodge vehicles, especially models like the Neon with a 2.0L SOHC engine, auto obd2 code p1390 typically points to a “Timing Belt Skipped One Or More Teeth.” This discrepancy highlights the importance of considering your vehicle’s make and model when interpreting OBD2 codes. For our discussion, and focusing on the context of recent timing belt work, we will address P1390 as a timing-related code.
Symptoms Associated with P1390
When your vehicle throws the auto obd2 code p1390 related to timing, you’ll likely notice a few key symptoms:
- Check Engine Light: This is the most immediate indicator. The malfunction indicator lamp on your dashboard will illuminate, signaling a problem detected by the engine control unit (ECU).
- Poor Engine Performance: If the timing belt has indeed skipped a tooth or more, the engine’s valve timing will be off. This can lead to rough running, decreased power, and potentially misfires. However, if the skip is minor, the engine might seem to run “like a champ” as described, while still triggering the code.
Common Causes of P1390 After Timing Belt Service
After recently replacing the water pump and timing belt, and subsequently encountering the auto obd2 code p1390, several potential causes come into play:
- Incorrect Timing Belt Installation: Even for experienced DIYers, ensuring perfect timing belt alignment can be tricky. If the timing belt is not correctly positioned on the camshaft and crankshaft sprockets, even by a single tooth, it can trigger P1390. This is the most common suspect when the code appears immediately after timing belt work.
- Camshaft Position Sensor or Crankshaft Position Sensor Issues: While less likely immediately after a belt change unless disturbed during the process, problems with these sensors or their circuits can also lead to timing-related codes. A faulty sensor might send incorrect signals to the ECU, leading to a misinterpretation of the engine timing.
- Resurfaced Cylinder Head: A less common but plausible scenario, particularly if a significant amount of material was removed during cylinder head resurfacing, is a slight alteration in the distance between the crankshaft and camshaft. While typically minimal (like the mentioned 8 mil or 0.008 inches), some argue that this could theoretically affect valve timing enough to trigger a code in very sensitive systems. However, this is often debated and less likely to be the primary cause for P1390 in most cases, especially with a small amount of material removed.
Diagnosing and Addressing P1390
Here’s a step-by-step approach to diagnose and potentially resolve the auto obd2 code p1390 in your situation:
-
Verify Timing Marks: The first and most crucial step is to re-verify the timing belt alignment. You can do this by bringing the engine to Top Dead Center (TDC) on cylinder #1. Using a dowel or long screwdriver through the spark plug hole can help you find TDC accurately. Once at TDC, inspect the timing marks on your camshaft and crankshaft pulleys.
- Camshaft Sprocket Mark: Locate the timing mark on your camshaft sprocket. Often, there’s a notch or arrow that should align with a corresponding mark on the valve cover or cylinder head. In some cases, like the user mentioned, there might be an inspection hole with a rib. It’s important to confirm if this rib is indeed the intended timing mark for your specific vehicle. Consult your vehicle’s repair manual or reliable diagrams to confirm the correct timing mark location.
- Crankshaft Sprocket Mark: Similarly, check the timing mark on the crankshaft pulley. This usually aligns with a mark on the engine block or oil pump housing.
- Double-Check Alignment: Ensure both camshaft and crankshaft timing marks align simultaneously when cylinder #1 is at TDC. If the marks are off, even slightly, it indicates the timing belt is not correctly installed.
-
Sensor Inspection (Camshaft and Crankshaft Position Sensors): Visually inspect the wiring and connectors for both the camshaft and crankshaft position sensors. Look for any damage, loose connections, or corrosion. While less likely the direct cause immediately after belt replacement, sensor issues can still contribute to timing discrepancies.
-
Consider a Relearn Procedure (With Caution): Some vehicles, after timing-related repairs or sensor replacements, might benefit from a “crankshaft position relearn” procedure. This allows the ECU to recalibrate and accurately read the crankshaft position sensor signal. However, for a P1390 code specifically related to “Timing Belt Skipped,” a relearn procedure is unlikely to be a fix for a mechanical timing issue. It’s more relevant for fine-tuning sensor readings after sensor replacement. If mechanical timing is incorrect, a relearn will not resolve the underlying problem. Dealer diagnostic tools or advanced scan tools are typically required for relearn procedures if they are applicable to your vehicle and situation.
-
Professional Diagnostic Assistance: If you’ve carefully checked the timing marks and are confident in the belt installation but the P1390 persists, or if you are uncomfortable performing these checks yourself, seeking professional help is advisable. A qualified mechanic can use advanced diagnostic tools to further investigate the issue, including sensor testing and potentially more in-depth timing analysis.
Conclusion
The auto obd2 code p1390, especially in Dodge vehicles, strongly suggests a timing-related problem, often stemming from incorrect timing belt installation. Thoroughly verifying the timing marks is the primary step in diagnosing this issue. While sensor problems or, less likely, head resurfacing might contribute, ensuring correct mechanical timing is paramount. If you’re a DIYer, double-checking your timing belt work is crucial. If the problem persists, don’t hesitate to consult a professional for expert diagnosis and repair. Correct valve timing is essential for engine health and performance, so addressing P1390 promptly is vital.
