How to Fix P1689 Code On Cummins? (Completely Explained)

The Diagnostic Trouble Code (DTC) is categorized for quick response for identifying the exact issues of a vehicle. Among many variables showing similar data for multiple causes, the OBD-II scanning in your Cummins helps narrow down to pinpoint the issue.

If your Cummins experiences the DTC P1689 code, the engine is not getting enough pressurized gas through the fuel injector pumps. It mostly happens when the electronic communication between the control modules is disrupted within the vehicle’s powertrain system.

There is nothing to worry about if you are new to this error code in your Dodge Cummins. This article would be helpful for you in revealing the symptoms, causes, and potential fixes for the P1689 error code.

What Does P1689 Code Mean On Cummins?

The P1689 is the specific error code showing malfunction between the communication bridge of the Engine Control Module (ECM) and Fuel Pump Control Module (FPCM).

Breaking down the P1689 DTC reveals in the following way.

  • P = Powertrain, the system of components that propels your car forward (In our case, this is the transmission).
  • 1 = Manufacturer Specific Code (Dodge Cummins)
  • 6 = Computer Auxillary Outputs
  • 89 = Specific fault index (In our case, this denotes low fluid pressure)

There is a chain of command between different components inside Cummins. When a secondary powertrain module fails, the ECM shows false data, and hence the truck fails to deliver the expected performance.

How Serious Is P1689 Code On Cummins?

If your Cummins shows a P1689 diagnostic trouble code in the OBD-II scanner, you should seriously consider it. This fault can cause some major damage to the primary components of the powertrain system of the truck.

Besides, the truck’s performance will degrade day by day if you drive the Cummins with P1689. You will lose acceleration while overtaking, engine stalling on the road, and some other problems due to P1689.

Moreover, driving a vehicle with the Check Engine Light being turned on violates the law for vehicle engine fitness. As a result, you can get in trouble with the cops for violating transportation laws and need to pay a huge amount of fines.

Since P1689 illuminates two major malfunctions, which are either in the FPCM or the ECM. It should be thoroughly diagnosed and fixed because late fixation can be very steroid and expensive.

What Causes P1689 Code On Cummins?

The P1689 code is derived from the Computer Auxillary output errors in the Cummins. It can happen due to a lot of factors between the Fuel Pump, Fuel Injector, Fuel Pump Control Module, and the Engine Control Module. The most common causes for the P1689 are as follows:

  • The fuel pump is Not Functioning properly
  • Defect in the Fuel Pump Control Module (FPCM)
  • Damages in the electric harness, wiring, and connecting pins.
  • Defect in the Engine Control Module (ECM)
  • Damages in the wirings, fuse, and harness on the ECM side
  • Fault in the electrical circuit
  • Damages in the programming or circuitry of the Powertrain Control Module (PCM)
  • Contaminated fuel filter
  • Low-grade fuel
  • Driving in Low fuel condition

How To Fix P1689 Code On Cummins?

To fix the p1689 engine error code, you must look into the fuel injection system. The low pressure from the fuel pump in the injectors needs to be fixed. Besides, you also need to fix the oil pressure control solenoid’s improper functioning.

Acquiring Freeze frame Data

First, it is important to get the freeze frame data from the OBD-II scanning to confirm the error. Connect the PC connector to the OBD-II scanner tool/laptop and start the diagnostic.

When finished, check the DTC and confirm it is P1689. Save the Freeze Frame Data for further assessment.

Step 1: Initial and Visual inspection

Open the hood and inspect all the fuel pump control module and engine control module connections. Check if the wiring is broken, spliced, or burned up. If connections are missing, mark them and repair them.

Besides, the connecting pins can be broken, bent, or corroded. For such cases, replacing the pins is required to solve the issue. You may need to install new pair of connecting wires to rejoin the bridge between the FPCM and ECM.

Step 2: Checking harness, wirings and connectors

Locate the Engine control module and check the harness of the connections visually. If you find any anomaly during the visual inspection, follow the wiring codes from the service manual to restore the connections.

Step 3: ECM Programming Inspection

Sometimes the ECM programming for the pressure input in the fuel pump changes, causing the P1689. Inspect the coding through diagnostic tools, laptops and restore it the factory way.

This will reset the connection between the ECM and FPCM to communicate properly, and better fuel pressure will be observed.

Step 4: Checking Fluid Transfer Media

If the problem continues, you need to check the transferring inlet of the gas from the injector to the engine. Obstruction on the path of the fuel results in low pressure in the combustion chamber.

Step 5: Battery And Other Power Source Mediums

Check the battery connector to the circuit connecting the FPCM and ECM. If everything is working fine, you may need to replace the Fuel Pump Control Module. It is better to seek the help of a professional for the replacement.

Other Symptoms Of Getting P1689 Code On Cummins

When you Cummins have a  P1689, there are some major and minor symptoms using which you can confirm the issue. These symptoms are as follows:

  • Check Engine Light Turns On and remains On until the problem is fixed
  • The RPM does not get high. Sometimes it gets locked between 1300 to 1400 RPM
  • Lack of acceleration when required
  • Decrement in the top speed of the vehicle.
  • The engine gets stalled whenever you try to accelerate
  •  Rattling noise from the engine or exhaust of the vehicle
  • Sudden jerks and bounces from the engine while pushing the pedals

How Much Does it Cost to Fix the P1689 Code?

Workshop costs can vary depending upon the location and type of instruments required to fix it. Besides, the vehicle type, making year, and parts availability also determine the fixation cost of P1689.

It is an inexpensive issue; therefore, you will get the parts for around $100 to $250. But if the fuel injection control module requires replacement, you need to pay more than $600 for the part itself. The service charge varies from $75 to %150 per hour.

Can You Drive Your Cummins With code P1689?

The P1689 is indirect engine trouble. You can drive your vehicle with this code since it allows the engine to ignite. But you will not get the expected acceleration and RPM over 1400 in worst-case scenarios.

Therefore, driving the Cummins with such defects is very dangerous, especially on the freeway.

Your engine may also get suddenly stalled while accelerating. That is why it is not recommended to drive Cummins with P1689. However, you can drive a short distance to get your vehicle to the workshop.


The P1689 can cause major trouble in the engine if not fixed on time. Besides, the expense may get elevated with time. Being a newbie about trucks, it is okay to wonder what is code P1689 means on Cummins.

But we hope you have understood the symptoms, causes, and probable fixes of the P1689 trouble code for your vehicle from this article.

It will help you take quick decisions to overcome the problem and save a lot of money for other side problems caused by P1689.

Related Posts:

Similar Posts