p1391 loss of cam or crank

P1391 Loss Of Cam Or Crank? Explained!

Have you suddenly encountered a code on your dashboard during an intense long drive? The code is notifying the P1391 cam or crank? But don’t you even have a mere idea what this code means?

Then what does the P1391 cam or crank mean?

P1391 cam or crank means intermittent loss of CMP (camshaft) or CKP (crankshaft) in some brands of cars, such as; Jeep, Dodge, Chrysler, etc. In the OBD II, this code indicates that the camshaft or crankshaft position sensor is malfunctioning. Apart from that, the wiring issue between the sensor and PCM, timing belt/chain skipped tooth, faulty PCM and BCM, etc. can be the reasons. 

Basically, this is just a quick overview. For more information, continue reading. 

What Does P1391 Loss Of Cam Or Crank Mean?

P1391 loss of cam and crank is actually an OBD diagnostic trouble code. For some brands of cars, this code indicates issues with camshafts and crankshafts.

Have a quick look at the table below to know which brands of cars mean cam and crank problems by this code.

ManufacturerOBD II- P1391 Code Meaning 
Jeep, Dodge, Chrysler, Mitsubishi, PlymouthIntermittent loss of CMP or CKP

Other than these brands of cars, other manufacturers mean other sorts of problems by this code.

How Serious the P1391 Code Is?

As you already know what the P1391 loss of cam or crank means, now it’s crucial to know how serious this problem is. Depending on the issue that caused the P1391 code to be triggered, the severity of the code can vary.

In some cases, the error code does not cause any noticeable symptoms or drivability issues, and the vehicle can be driven as normal. 

However, sometimes, the code may cause the engine to run poorly or stall, and the vehicle may be difficult to start or may not start at all.

If the code is caused by a problem with the camshaft or crankshaft position sensor, the engine may be damaged if the issue is not addressed in a timely manner. The engine may stall or not start at all, which could cause the loss of control of the vehicle.

Reason and Fixes of P1391 Loss Of Cam Or Crank

P1391 loss of cam or crank may arise due to certain reasons. Take a look at the table below for detailed guidance.

Reason for P1391 CodePossible Fixes
Camshaft or crankshaft position sensor malfunctionReplace camshaft crankshaft position sensor
Wiring issue between the sensor and PCMInspect and repair wiring and connections
Failed PCM or BCMReplace PCM or BCM
Timing belt or chain skipped a toothInspect timing belt/chain and related components, replace as necessary
Failed valve lifterReplace valve lifter

You’ll encounter the following possible symptoms of P1391 loss of cam or crank if this stores the above issues.

  • Engine may not start or may stall while driving
  • Reduced engine power or performance
  • Check Engine Light (CEL) is illuminated
  • Rough idling or misfiring
  • Difficulty starting the engine
  • Poor fuel economy
  • Engine may make unusual noises

Now let’s get into the deep discussion of problems and solutions.

Reason 1: Camshaft or Crankshaft Position Sensor Malfunction

The camshaft or crankshaft position sensor transfers signals to the dashboard if these are working correctly or not. When the sensor is defective it can’t transfer the signal correctly to the system.  Due to this P1391 loss of cam or crank may appear. 

Solution: Replace Camshaft or Crankshaft Position Sensor

If the P1391 trouble code stores for the defective camshaft or crankshaft sensor you need to replace them as soon as possible. Replacing the cam or crank sensor is a complex task. So it’s better to take assistance from a professional mechanic to replace it. 

Reason 3: Wiring Issue Between Sensor and PCM

Wiring is the media to connect the PCM (powertrain control module) and the camshaft and crankshaft sensor. If the wire is corroded or damaged then it can’t transfer signals correctly. This is another potential cause that can occur with the P1391 trouble code. 

Solution: Inspect And Repair Wiring And Connections

If the P1391 trouble code stores due to a wiring issue, you need to inspect and replace or fix the wire corrosion. To inspect and fix the wiring issue between the PCM (Powertrain Control Module) and the camshaft or crankshaft sensor, you will need to follow these steps:

Step 1: Find the PCM and camshaft/crankshaft sensor

PCM and camshaft/crankshaft sensor can typically be found near the engine, but the exact location will vary depending on the make and model of the vehicle.

Step 2: Inspect the wiring

First, visually inspect the wiring between the PCM and the sensor for any visible damage, such as frayed wires or loose connections. 

Then use a multimeter to check for continuity in the wiring. If the continuity is not present, the wiring may be damaged and will need to be repaired or replaced.

Replacing the wire is a difficult task, you must have knowledge of the wiring diagram. Also to replace the wire you might need to unscrew some crucial components. For this kind of task, you must take the assistance of a professional automobile mechanic unless you’ve enough experience to do so. 

Step 3: Clear the error code

Clear any diagnostic trouble codes that have been stored in the PCM, and test drive the vehicle to verify that the issue has been resolved.

Reason 4: Failed PCM or BCM

When the Powertrain Control Module (PCM) or Body Control Module (BCM) detects a failure in the Camshaft Position (CMP) sensor or Crankshaft Position (CKP) sensor, it will store a diagnostic trouble code (DTC) P1391 in its memory. 

This DTC indicates that there is a loss of signal or a malfunction in the sensor, which can affect the engine’s performance and fuel efficiency. 

To diagnose and fix the problem, a mechanic will need to retrieve the DTC from the module’s memory using a diagnostic scanner. Then the sensor and its related wiring and connections need to be inspected for any issues. 

Solution: Inspect And Repair Wiring And Connections

We’ve already discussed how to inspect and repair wiring and connection. So for the guide on how to do it follow the steps mentioned in the above section.

Reason 5: Timing Belt Or Chain Skipped Tooth

The timing belt or chain is the most important component for the camshaft and crankshaft. If the timing belt fails or skipped teeth that can occur P1391 loss of cam or crank issues. 

Because the timing belt/chain synchronizes the timing between the camshaft and crankshaft. If it skips the tooth then the cam or crank sensor transfers the error signal. 

The purpose of this message is to inform you that there are problems with the system.

Solution: Inspect and Replace the Timing Belt/Chain

Timing chains typically don’t have this type of issue. However, if you encounter this type of issue in the chain you may need to consult a professional automobile mechanic.  

On the other hand, the timing belt can skip the tooth due to wear and being stretched. In this case, you need to replace the timing belt. To replace the timing belt follow the steps below.

Tools Needed:

  • A new timing belt 
  • A socket wrench set
  • A ratchet
  • Screwdriver
  • Tension arm 
  • Tension gauge

As you now have these pieces of equipment ready, let’s jump onto the steps to replace the timing belt.

Safety precaution: Remember to disconnect the battery to avoid any electrical hazards. The negative terminal should be removed first, followed by the positive terminal. Follow these steps in reverse order when you are ready to reconnect the battery.

Step 1: Take The Serpentine Belt Off

The serpentine belt is located on the timing belt cover. To access the timing belt, you must first remove the serpentine belt. 

To do this, turn the bolt of the serpentine belt tensioner pulley clockwise using the tension arm. Once the belt is loosened, it should easily come off the pulley. For a visual guide, see the image below.

Serpentine Belt Off
Source: Throttle

Step 2: Take Off The Timing Belt Cover

Use a wrench set and screwdriver to loosen and remove all the nuts and bolts that keep the cover in place. The timing belt can then be accessed once that’s done.

Step 3: Loosen The Tensioner Pulley To Remove The Timing Belt

To begin, you must find the timing belt tensioner pulley, which is typically situated in the central area between the camshaft and crankshaft. 

Use a ratchet or tension arm to turn the tensioner pulley bolt clockwise. As you continue to loosen the belt tension, after that you’ll be able to pull it off.

Step 4: Adjust Alignment & Install The New Timing Belt

Now, the timing belt needs to be installed correctly. Before you install the timing belt make sure all the camshaft and crankshaft pulleys are correctly aligned.

To align the pulleys in the correct order rotate the crankshaft and camshaft with a long ratchet and keep all the timing marks on the pulleys in an identical direction. For a visual understanding see the image below.

Timing Belt

Now, simply install the timing belt on the pulleys and make sure the belt teeth are correctly placed on the pulleys. 

Step 5: Adjust The Timing Belt Tension

Use the tension arm to rotate the timing belt tensioner pulley in a counterclockwise direction to tighten the timing belt to the specified tension. 

Next, check the tension on the timing belt with a gauge and adjust it according to the manufacturer’s recommendations. Check out the video for a tutorial if you’re not sure how to do this.

Note: It’s a good idea to replace the tensioner pulley with a new belt for improved durability and better performance.

Step 6: Cross-Check the Timing Belt Tension

After adjusting the tension on the timing belt, start the engine to see if it’s working properly. 

After running the engine for a while, check the tension on the timing belt again using the process described in step 5. If you notice any problems with the tension or alignment, go back and repeat steps 4 and 5.

Step 7: Reassemble The Parts

To finish up, just put all the parts back on following the order you removed them. You should double-check everything to make sure it is where it should be. And that’s it! you’re done with the whole procedure.

It is a complicated process to replace a timing belt. Unless you have sufficient experience, you should seek professional assistance.

Reason 6: Failed Valve Lifter

The valve lifter sits on the camshaft and transfers valve opening and closing motions to the pushrods and rockers. 

As the valve lifter is directly connected to the camshaft that’s why when it fails, the camshaft sensor can transfer the “P1391 loss of cam or crank” signal. 

Solution: Replace Valve Lifter

Replacing the valve lifter needs very technical skills and knowledge. So it’s always recommended to contact an automobile expert to do it. 

How Other Manufacturers Define OBD II P1391 Code?

P1391 trouble code is used by some manufacturers to indicate a cam or crank issue. However, this code is not defined the same way across all manufacturers.

Have a look at the table below to know how other manufacturers define P1391. 

ManufacturerOBD II- P1391 Code Meaning 
Citroen, Peugeot, Ford, Lincoln, Mercury, Oldsmobile  Glow Plug Circuit Low Input (Bank #1)
GM, Volkswagen, Audi, VolvoWheel Speed Sensor 1 – G – Sensor Circuit Performance
IsuzuG Sensor Performance

As you can see, P1391 doesn’t mean the same thing to all manufacturers. To know how to fix trouble code you can check out the methods of fixing trouble code.

Frequently Asked Questions (FAQs):

How Do I Reset My Camshaft Sensor?

To reset the camshaft sensor first disconnect the negative battery terminal and then wait for at least one hour, this will reset the ECU. Then reconnect the battery and clear any error code stored in the vehicle’s computer. 

Does The Camshaft Sensor Affect Idle?

Yes, the camshaft sensor pulley affects idle. This is because the camshaft and idler pulley are connected by the timing belt or chain. When the camshaft sensor fails it causes rough idling. 


Well that’s all about “P1391 loss of cam or crank”. Hopefully, you’ve got all the answers you expected from this article. Anyway, if this trouble code is stored you should get rid of it as early as possible. 

Thanks for reading!

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *