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Code P1391 Dodge. Intermittent CMP or CKP signal condition

The P1391 code dodge is defined as an intermittent CMP or CKP signal condition. It refers to problems in the signal from the camshaft position sensor or the crankshaft position sensor and is a specific failure for Dodge and Jeep brand models.

P1391 is one of those fault codes that you wouldn’t want to have. While its symptoms are few, its implications are quite serious when left unaddressed, and the potential causes are almost limitless.

Additionally, your triggers are highly app-dependent, something this guide will help clarify.

Operation of CMP and CKP Sensors

CMP and CKP sensors (or camshaft and crankshaft position) serve as informants and messengers for the PCM/ECM.

They provide your car’s computer with crucial information about camshaft speeds and the like that helps determine the proper ignition and fuel injection timing the machine requires.

The inability of these sensors to send accurate data (or any type of information) to the PCM would cause the system to malfunction. Of course, these sensors fail over time or due to normal wear and tear.

Adverse accidents or manufacturing errors can also be causes of this error.

What Is Code P1391 Dodge?

Error code P1391 occurs when the PCM (Powertrain Control Module) has detected that the actual position of the CMP or CKP is not in accordance with the expected level set by the manufacturer.

This error code is not a generic code. Its definition may vary from one model to another. Dodge and Jeep but it will always refer to signal problems with these two sensors.

Its symptoms include an activated Check Engine light, erratic engine performance, and no start.

Common Symptoms of Code P1391 in Dodge

Your car may or may not activate the code P1391 depending on the situation. In this case, a scanner would be useful. However, it would be best if you are aware of the signs that indicate in advance an impending problem with one of the sensors.

That being said, let’s look at some of the symptoms:

1. Check the engine light on

Like most other error codes, a faulty CMP or CKP sensor activates the Check Engine light. And like the others, it’s not automatically the root cause of this.

You will need to determine what system or vehicle function has caused the sensor to become faulty and continue from there.

Using a scan tool should show multiple fault codes if there are multiple reasons behind this indicator. Code errors are likely to appear accompanying P1391.

Knowing how to identify the fault by the combination of codes can save you time in the diagnosis.

You may also be interested in Code P1345 General Motors. Correlation Between Crankshaft Position and Camshaft Position

2. Failure to start and loss of power

Although very common, starting difficulties are actually a consequence of ignoring the above symptoms of the code P1391. For example, starting in two or three attempts and believing that it is normal because the car is “Cold”.

Then, over time, the fault worsens and ends up disabling the car. A P1391 code can affect the initial start of the car so much that it can disable it completely.

This makes a lot of sense since a weakened camshaft sensor would not be able to transmit enough signal to the PCM. It also strongly suggests a potential problem with the crankshaft sensor when the no-start problem is characterized by long cranking times.

3. Loss of power

If you leave the problem unattended for too long, the signal loss between CMP and CKP sensors with the PCM becomes more evident. This loss of signal does not allow good synchronization, causing the engine to lose power.

The loss of power in the engine is serious since it can affect other expensive mechanical components of the engine. Furthermore, no one wants to drive a car feeling that its performance has diminished.

4. Frequent stops or irregular idling

Irregular or unpredictable engine performance, such as rough idling or slow acceleration, is a telltale sign of a faulty CMP sensor.

While these symptoms gradually increase, it would be much better to address them early on and diagnose exactly what the fault is.

Delaying these can cause your engine to shut down or, worse yet, your vehicle to abruptly shut down in the middle of nowhere. But be careful, these symptoms also point to other car problems, such as lack of fuel and the like.

Therefore, careful diagnosis is recommended.

Possible Causes of Code P1391 Dodge

Unlike its number of symptoms, many factors can cause your vehicle’s CKP and CMP sensors to become damaged. In some cases, the sensors are very worn, in other cases, the culprit is your car’s electrical circuit.

Getting an immediate look at these two is almost an expectation. But if you think it’s something else, consider the following when narrowing down the root cause of a P1391 code:

  • Carbon-filled IAC valve.
  • Dirty reluctor for CMP sensor.
  • Metal debris or other obstructions stuck in the CKP sensor.
  • Stretched or loose timing belt or chain.
  • The CMP sensor is out of sync.
  • The CKP sensor is physically in contact with the steering wheel.
  • Blown fuses in the control circuit.
  • Low battery voltage.
  • Defective CKP.
  • CKP sensor harness open or shorted.
  • Bad electrical connection at the CKP sensor.
  • CMP sensor harness open or shorted.
  • Bad electrical connection on the CMP sensor.

Distributor Problems On Jeep Models

Code P1391 on Jeeps deserves a separate section. It is usually activated when the distributor or cam sensor assembly is incorrectly phased.

A Jeep owner may have their engine upgraded to a long block but still paired with their old distributor, therefore, with timing off.

Or there may be excessive wear on the distributor teeth, which is typical of high-mileage Jeeps.

Fortunately, the first scenario is an orientation problem and can be solved by installing an alignment pin while making sure the distributor is at the correct timing.

The second, on the other hand, warrants a replacement. Also, consider that since the PCM controls all timings, a good distributor with a bad PCM would produce the same code.

Be sure to opt for genuine OEM Jeep parts whenever possible.

How to Diagnose Code P1391 Dodge

Below are the steps to diagnose an error code P1391:

1. Check the fault code log

Using a scanner records all fault codes that occur along with the P1391 code, as well as frozen data. If there are other error codes, be sure to resolve them first.

Clears the other codes in the order they were stored before diagnosing P1391. The scanner can be a higher specification OBD-II or DRB-III tool to complete this step.

2. Examine the wiring

Examine the wiring and connectors for burn marks, arcing, oxidation, damage, or disconnection, so you don’t have to deal with out-of-spec resistance/ground readings later.

Consult your owner’s manual for routing specifications and color codes to make it easier to locate relays, fuses, or other potentially involved components.

Also, keep in mind that detection of any of these defects requires immediate replacement of the part.

Once you have ensured that the electrical system is fully functional, proceed to investigate the faulty sensor, be it the CMP or CKP.

3. Perform checks

Perform resistance and continuity checks on all system fuses. Also, check ground and reference voltages as necessary.

Check the actual readings against the OEM specifications in the manual, and replace any relays found to be faulty.

To ensure there is no damage, disconnect the relevant sensors from the PCM before performing these checks. After testing or replacing the relay, rescan the system and see if the P1391 code clears or persists.

4. Test the sensors

Check the input and output voltage of each sensor, as well as its resistance and continuity. For this, you must use a digital multimeter that you can configure to voltage, resistance, and continuity respectively.

If you detect anomalies in the sensor, you must proceed to change it. Sensors are generally not repairable; you just need to replace them with an original OEM replacement.

5. Repeat the tests

At this point, you should have already determined a part that needs repair or resolved the issue completely.

But if the code P1391 still appears, even though there is no visible damage and all the previous steps were verified, perform the same tests, but on all associated wiring.

How to Fix Code P1391 Dodge

Have you changed sensors recently? If so, then the sync may be out of date, which is causing this issue.

If you replaced the sensors and checked the wiring, the next thing you should check is the timing, and that includes removing the covers and performing a deep check on the system.

You should test the timing chain and make sure the timing mark is aligned. This is usually the most common scenario and relatively easy to fix.

The terminals on the sensor connector tend to separate, meaning that if the female terminal on the wiring harness becomes too loose, it will not be able to reliably connect to the male terminals on the sensor.

To inspect, remove one of the male electrical terminals from your old sensor, hold that terminal with your fingertips, and test for physical resistance and friction by carefully inserting each into the connector cavities on the side of the harness.

Otherwise, you will have to splice in a new connector.

Other repairs include:

  • CKP sensor harness repair or replacement.
  • Repair or replacement of electrical connection in CKP sensor.
  • CMP sensor harness repair or replacement.
  • Repair or replacement of electrical connection in CMP sensor.

In many cases, this problem arises from unreliable aftermarket sales parts. Therefore, it is always advisable to install original OEM sensors, as they are more reliable and fit your car perfectly.

Is Code P1391 Serious?

Yes, any failure related to engine performance can be considered serious. The car may initially start and you can drive it with code P1391 Dodge activated, but over time, the symptoms will worsen and may leave you stranded.

Ideally, you should diagnose and repair as soon as possible. This way you will avoid major failures that involve wasted time and money.

How Can I Avoid Code P1391 in Dodge?

A routine checkup and maintenance performed according to the manufacturer’s guidelines can prevent many headaches, including the appearance of the P1391 Dodge code.

Checking the condition of the cables, and connections, timely changing the timing belt or chain, and checking the sensors, are part of the routine activities that you should do in your car.

Conclusion

You may also be interested in Error Code P1340 – CKP/CMP Sensor Signals Out of Sequence (Audi, VW)

Whether the culprit is the CMP or CKP sensors, the control circuit, or the PCM, it’s worth having a scan tool, a multimeter, and your service manual nearby.

Anyone who has little knowledge on the subject will advise you to never perform diagnostics if you are inexperienced. And if you’re up to the task, you’ll know the importance of opting for OEM sensors and genuine replacement parts.

If you want to know other articles similar to Code P1391 Dodge. For intermittent CMP or CKP signal conditions, you can visit the category Fault Codes.

 

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