P1391 Dodge Ram 1500? What Are the Causes & How To Fix It?

The P1391 Dodge Ram 1500 is one of the unwanted trouble codes. Although its symptoms are unclear, its effects may be serious if you ignore them.

This DTC code often originates from different causes but mostly from the issues in the crankshaft or camshaft position sensor.

This article will help you identify the most prevalent culprits of this code with the best fixes.

Keep reading for more details!

What Does the P1391 Code Mean?

p1391 dodge ram 1500

It is a trouble code that indicates a problem with the camshaft position (or CMP) sensor, crankshaft position (or CKP) sensor, and even both.

Besides, this code also warns of the failure of the G-sensor in some car models – the vertical acceleration sensor with gravity sensing.

You may find various cases where this trouble code appears, depending on your vehicle manufacturer and type.

What Are the Causes Of the P1391 Dodge Ram 1500?

The P1391 error code on Dodge Ram can stem from multiple reasons, such as a faulty cam or crankshaft position sensor, insufficient input voltage, bad wiring between sensors and PCM, and poor G-sensors.

Besides,  malfunctioning PCM or BCM, chain skipping a tooth or failed timing belt, and bad valve lifter may also be the sources of this code.

Malfunction Crankshaft Position Sensor

Crankshaft sensors send signals to your vehicle’s dashboard as to whether they function properly. If the sensors are defective or worn-out, they may not deliver precise data to the car computer.

This could result in a p1391 Dodge Ram, and you have to replace the crankshaft sensors.

Faulty Camshaft Position Sensor

This is the main reason for the code P1391. Its obvious sign is CMP becomes shorted with the poor electrical connection.

Also, the intermittent condition in the camshaft position sensor will trigger this trouble code. Thus, you should monitor when CMP has any abnormal problems and get the proper repair.

If your car still gets the code after replacing the CMP, click here to learn the reasons and fixes.

Insufficient Input Voltage

P1391 code Dodge will pop up if the PCM in your vehicle detects the low input voltage in the control circuit of the glow plug.

You shouldn’t overlook the problem with the glow plug to identify the root cause of this trouble code.

Faulty Wiring Between PCM & Sensor

Wiring links the PCM (Powertrain Control Module) with the crankshaft and camshaft sensors.

Therefore, the corroded or failed wires can no longer properly transmit signals. This also is one of the possible causes of the P1391 Dodge code

G-Sensor Performance Issues

Dodge p1391 code may appear if there are any failures with G-sensor performance. Yet, assuming sensor failure when this error code first appears is not always the case.

Abnormal spikes in vertical acceleration can trigger this code. This is a natural result of transmission line deviation, misfires, or potholes.

Driving in rough terrain conditions can lead to the trouble code P1391.

Also, the G-sensor may share the same PCM voltage with the ground connection of the AC pressure sensor, so root cause identification isn’t easy.

Failed BCM or PCM

When the body control module (BCM) or the powertrain control module (PCM) detects a camshaft position (CMP) sensor or crankshaft position (CKP) sensor failure, it stores diagnostic error code p1391 Dodge in memory.

So once the BCM or CMP goes wrong, the code will appear. This trouble code indicates a signal loss or sensor failure affecting fuel efficiency and engine performance.

If you take your Dodge Ram to the auto shop, the mechanic will use a diagnostic scanner to diagnose the trouble code in the memory to fix it.

Besides, they help you check the sensor, connectors, and wires related to this code to solve the problems.

Chain Skipping A Tooth or Bad Timing Belt

The chain tooth or timing belt is the most important part of camshafts and crankshafts.

So, a failing timing belt or missing teeth can cause the Dodge code p1391 to experience cam loss and crank problems.

Because the toothed chain or timing belt synchronizes the control time between the crankshaft and camshaft, the crank or cam sensor will be at fault if these parts skip a tooth.

Poor Valve Lifter

The poor valve lifter is another cause of code p1391. The valve lifter lies on the camshaft and transmits the closing and opening movement of the valve to the lifter and rocker’s arm.

Since the valve lifters are connected directly to the camshaft, a failure can force the camshaft position sensor to send a “P1391 Crank or Cam Loss” signal.

What Are Symptoms of P1391 Dodge Ram 1500? 

p1391 dodge dakota

The first sign is an illuminated check engine light that indicates CKP or CMP sensor failure.

Besides, your vehicle that is difficult to start and suddenly stalls is one of the early symptoms of the P1391 error code.

In addition, if the engine behaves erratically or unpredictably, including sluggish acceleration or rough idle, it’s a clear symptom of a bad CMP sensor with code P1391.

This symptom of white smoke is mostly related to coolant leaks and can also occur when the car is started on a cool day. Yet, if the problem is recurring, the P1391 code might be to blame.

How to Fix P1391 Dodge Ram 1500? 

1. Check related TSB:  inspect the appropriate TSB (Technical Service Bulletins) for existing problems with your vehicle.

2. Note the error code: In this step, I used an OBD-II scanner to detect any trouble codes and freeze frame data appearing along with the P1319 code.

3. Inspect the parts, including connectors or wires, for corrosion, burn mark, damage, or saturation.

4. Conduct a continuity exam to check the fusible links or all fuses. Also, inspect the reference voltage and ground if necessary.

5. Run a sensor test to identify the failure with the glow plugs if you see the code P1391.

6. Test the wiring to relay if the error code persists and repeat the test to double-check if the components need fixing. 

7. Check the voltage at which the glow plug relay operates. Measurements need to match OEM values.

8. Perform the glow plug wire test in the system with the control module.

9. Continue checking glow plug resistance after checking all other suspect components.


dodge code p1391

I’ve covered the possible causes of the trouble code P1391 Dodge Ram 1500 with the complete guide on diagnosing and fixing it.

One of the main culprits that result in this code is malfunctioning CKP or CMP sensors.

Besides, this code can also stem from the low input voltage, failed wiring, poor G-sensor, bad timing belt, or valve lifter.

It’s essential to detect the code’s symptoms to find the best method for fixing it and protect your vehicle from more serious damage.

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