CM850 Electronic Control System – FAULT CODE 2266

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Overview

Electric Fuel Lift Pump Circuit SMALL | MEDIUM | LARGE

Circuit Description

On 12 VDC Automotive and 24 VDC Industrial or Marine systems, the circuit is a pulse width modulated driver in the electronic control module (ECM) that controls the electric fuel lift pump. The lift pump is grounded in the ECM.

On 24 VDC Automotive systems, the circuit is a pulse width modulated driver in the ECM that controls the electric fuel lift pump relay. The circuit includes two additional components, a relay and voltage regulator. The ECM controls voltage to the relay. When the relay is engaged, an OEM supplied power source delivers 24 VDC to the voltage regulator. The voltage regulator reduces the 24 VDC to 12 VDC, which is then delivered to the lift pump.

Component Location

On both 12 and 24 VDC systems, the electric fuel lift pump is located behind the ECM cooling plate on the intake side of the engine. Refer to Procedure 100-002 for a detailed component location view.

On 24 Automotive VDC systems, the relay is located in the harness between the voltage regulator and the OEM power supply on the bottom edge of the ECM. The voltage regulator is located just below the ECM.

Shop Talk

This fault code becomes active whenever the ECM detects a short circuit to ground or high current in the electric lift pump circuit. Causes for this fault code are short circuit to ground or low resistance.

On 12 VDC Automotive and 24 VDC Industrial or Marine systems during cold weather, gelled fuel can plug the lift pump and cause this fault code. Listen to the lift pump to be sure it is running during cold ambient temperatures (less than -29°C [-20°F]). This fault code can also become active if the lift pump rotor stalls or seizes. When the fault conditions are detected, the ECM driver to the lift pump is turned off to protect the circuit. It is necessary to cycle the keyswitch OFF and then back ON before the ECM will retest for the cause of the fault code. The ECM driver is re-enabled at keyswitch ON, and if the cause is no longer present, the fault code will become inactive and can be cleared.

On 24 VDC Automotive systems, the ECM driver to the lift pump relay is turned off when a short circuit to ground or high current in the electric fuel lift pump wiring harness relay circuit is detected. Causes of this fault code are a short circuit to ground or high current in the electric fuel lift pump wiring harness, relay or engine harness. This fault code will not become active if the voltage regulator or electric fuel lift pump has failed.

NOTE: On 12 VDC systems, this fault code will also become active if the priming pump motor stalls. Stall current for the priming pump motor is approximately 9 amperes. A good priming pump typically runs with less than 3 amperes. If the fault code is intermittent, observe the snapshot data priming pump measured current. If current was near 9 amperes when the fault condition occurred, conclude that the rotor has stalled and replace the electric priming pump.

Refer to Troubleshooting Fault Code t05-2266