Error Code P1237 is defined as Fuel Pump Secondary Circuit Fault. This code happens when the fuel pump driver module has determined a problem in the fuel pump secondary circuit.

This error code is a generic trouble, meaning it applies to all vehicles equipped with OBD-II system, especially vehicles made since 1996 up to present. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.


The FPDM or Fuel Pump Driver Modules control the voltage to the Fuel Pump to help keep proper fuel pressure throughout the operating range of the engine. Error Code P1237 takes place when the FPDM has determined a problem in the fuel pump secondary circuit. The FPDM indicates to the PCM (powertrain control module, also known as ECM or engine control module in other vehicles makes) through the FPM (fuel pump monitor) circuit to highlight the detected concern. The PCM then sets the error code to the DTC and activate the Check Engine light to notify the driver of the problem.

Common Symptoms

The most common symptom and usually the only symptom for this error code is the activation of the Check Engine light and the registration of the error code. In other vehicle makes, the engine may not start at all.

Possible Causes

Error Code P1237 can be caused by multiple problems. Some of the most common possible causes include:

  • Defective (Fuel Pump Driver Module)
  • Open or Shorted Fuel Pump Driver Module harness
  • Poor electrical connection in the Fuel Pump Driver Module
  • Defective fuel pump (rare)

How to Check

Error code P1237 is usually quite easy to diagnose. Because it relates to fuel pump circuit, technicians start their diagnosis by checking the fuse and pump relay. If both are good, then the problem could be a case of failed fuel pump.

How to Fix

  • Replace defective fuel pump
  • Repair or replace open or shorted FDPM harness
  • Repair or replace poor electrical connection in the FDPM
  • Replace the defective FDPM

In many cases, the easiest way to fix this error code is to replace the defective FDPM.