Understanding the P1391 Camshaft or Crankshaft Code
Have you ever been on a long drive when suddenly a warning code appears on your dashboard? If you’ve encountered the P1391 cam or crank code and have no idea what it signifies, you’re not alone. This code can be alarming, especially if you’re unsure of its implications.
The P1391 code indicates an intermittent loss of the CMP (camshaft) or CKP (crankshaft) sensor in various vehicle brands, including Jeep, Dodge, Chrysler, and more. In the context of OBD II diagnostics, this code suggests that there may be a malfunction with either the camshaft or crankshaft position sensor. Additionally, wiring issues between the sensor and the PCM (Powertrain Control Module), timing belt or chain problems, and potential faults with the PCM or BCM (Body Control Module) could also be contributing factors.
For a more comprehensive understanding, let’s delve deeper into the specifics.
What Does the P1391 Loss of Cam or Crank Mean?
The P1391 code is essentially an OBD diagnostic trouble code that signifies issues related to the camshaft or crankshaft in certain vehicle brands. To clarify further, refer to the table below outlining the specific meanings attributed to this code by various manufacturers:
| Manufacturer | OBD II – P1391 Code Meaning |
| Jeep, Dodge, Chrysler, Mitsubishi, Plymouth | Intermittent loss of CMP or CKP |
It’s essential to note that other manufacturers may interpret this code differently.
How Serious is the P1391 Code?
Now that you understand what the P1391 code represents, it’s crucial to assess its severity. The seriousness of this code can vary significantly depending on the underlying issue causing it. In some scenarios, the error code might not lead to any noticeable symptoms or affect drivability, allowing you to operate the vehicle normally.
However, in other cases, the engine may exhibit poor performance, stalling, or even difficulty starting. If the code stems from a malfunctioning camshaft or crankshaft position sensor, neglecting the issue could lead to engine damage, resulting in stalling or a complete failure to start, which could compromise vehicle control.
Causes and Solutions for P1391 Loss of Cam or Crank
The P1391 loss of cam or crank can arise from several potential causes. Below is a detailed table outlining these causes alongside their corresponding solutions:
| Cause of P1391 Code | Possible Solutions |
| Malfunctioning camshaft or crankshaft position sensor | Replace the camshaft or crankshaft position sensor |
| Wiring issue between the sensor and PCM | Inspect and repair wiring and connections |
| Failed PCM or BCM | Replace the PCM or BCM |
| Timing belt or chain has skipped a tooth | Inspect timing belt/chain and related components; replace as necessary |
| Faulty valve lifter | Replace the valve lifter |
The following symptoms may indicate a P1391 loss of cam or crank:
- Engine may not start or may stall while driving
- Reduced engine power or performance
- Check Engine Light (CEL) illuminated
- Rough idling or misfiring
- Difficulty starting the engine
- Poor fuel economy
- Unusual engine noises
In-Depth Problem Analysis and Solutions
1. Camshaft or Crankshaft Position Sensor Malfunction
The camshaft and crankshaft position sensors are responsible for relaying critical signals to the dashboard. If either of these sensors fails, they may not communicate effectively with the vehicle’s system, potentially triggering the P1391 code.
Solution: Replace the Camshaft or Crankshaft Position Sensor
If a malfunctioning camshaft or crankshaft sensor is identified as the issue, timely replacement is essential. This process can be intricate, so it’s advisable to seek assistance from a qualified mechanic to ensure proper installation.
2. Wiring Issues Between Sensor and PCM
Wiring serves as the communication link between the PCM and the camshaft/crankshaft sensors. If the wire becomes corroded or damaged, it may fail to transmit signals correctly, leading to the P1391 trouble code.
Solution: Inspect and Repair Wiring and Connections
To address wiring issues, follow these steps:
- Step 1: Locate the PCM and Sensors: The PCM and sensors are generally situated near the engine; exact locations will vary by vehicle make and model.
- Step 2: Inspect the Wiring: Perform a visual inspection for any visible damage such as frayed wires or loose connections. Utilize a multimeter to check for continuity. If continuity is absent, repair or replace the damaged wiring.
- Step 3: Clear the Error Code: After repairs, clear any diagnostic trouble codes stored in the PCM and take the vehicle for a test drive to confirm the resolution of the issue.
3. Failed PCM or BCM
The PCM or BCM can store a P1391 code if they detect a failure in the camshaft or crankshaft position sensors. This situation can significantly affect engine performance and fuel efficiency.
Solution: Inspect and Repair Wiring and Connections
As previously discussed, inspecting and repairing wiring and connections is critical to resolving this issue.
4. Timing Belt or Chain Skipped Tooth
The timing belt or chain plays a crucial role in synchronizing the camshaft and crankshaft. If it skips teeth, it can trigger the P1391 loss of cam or crank signal.
Solution: Inspect and Replace the Timing Belt/Chain
While timing chains are less prone to this issue, timing belts can wear over time. If you suspect a skipped tooth, consider the following steps for replacement:
- Tools Needed: New timing belt, socket wrench set, ratchet, screwdriver, tension arm, and tension gauge.
- Step 1: Remove the Serpentine Belt: Loosen the serpentine belt tensioner pulley and remove the belt.
- Step 2: Remove the Timing Belt Cover: Unscrew all fasteners securing the cover to expose the timing belt.
- Step 3: Loosen the Tensioner Pulley: Use a ratchet to relieve tension on the timing belt.
- Step 4: Install the New Timing Belt: Ensure proper alignment of all pulleys before installing the new belt.
- Step 5: Adjust Timing Belt Tension: Tighten the belt to the manufacturer’s specifications.
- Step 6: Reassemble All Components: Replace all parts in reverse order of removal.
This process can be complex; if unsure, it’s best to consult a professional mechanic.
5. Failed Valve Lifter
The valve lifter is directly connected to the camshaft and plays a vital role in valve operation. A failure here can also lead to the P1391 code.
Solution: Replace the Valve Lifter
Replacing a valve lifter requires specialized skills, so it’s advisable to engage a professional mechanic for this task.
How Other Manufacturers Define the OBD II P1391 Code
While the P1391 code typically indicates a cam or crank issue for certain manufacturers, its definition can vary across different brands. Below is a table illustrating how various manufacturers interpret the P1391 code:
| Manufacturer | OBD II – P1391 Code Meaning |
| Citroen, Peugeot, Ford, Lincoln, Mercury, Oldsmobile | Glow Plug Circuit Low Input (Bank #1) |
| GM, Volkswagen, Audi, Volvo | Wheel Speed Sensor 1 – G Sensor Circuit Performance |
| Isuzu | G Sensor Performance |
As illustrated, the P1391 code does not hold a consistent meaning across all manufacturers, making it essential to understand specific interpretations for accurate diagnostics.
Frequently Asked Questions (FAQs)
How Do I Reset My Camshaft Sensor?
To reset the camshaft sensor, begin by disconnecting the negative battery terminal and allowing the vehicle to sit for at least one hour. This process will reset the ECU. Reconnect the battery and clear any stored error codes from the vehicle’s computer.
Does the Camshaft Sensor Affect Idle?
Yes, the camshaft sensor can significantly impact idle quality. Since the camshaft and idler pulley are interconnected via the timing belt or chain, a malfunctioning camshaft sensor can lead to rough idling.
Conclusion
In summary, the P1391 loss of cam or crank code signifies important issues that require prompt attention. By understanding its implications and potential solutions, you can take the necessary steps to address this code effectively. Thank you for taking the time to read through this comprehensive guide!