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Mechanical Gas Fuel System G5.9, G8.3 – FAULT CODE 121

Engine Speed Sensor Circuit Lost Signal from the Magnetic Pickup Sensor – Abnormal Rate of Change


Overview

Engine Speed Sensor Circuit

CODE REASON EFFECT
Fault Code: 121
PID: P190
SPN: 190
FMI: 10
LAMP: Warning
SRT: 

Engine Speed Sensor Circuit Lost Signal from the Magnetic Pickup Sensor – Abnormal Rate of Change.

Engine will shut down.
Engine Speed Sensor Circuit
SMALL | MEDIUM | LARGE

Circuit Description

The engine speed sensor provides the engine speed signal to the ECM through the engine harness.

Component Location

100-002 for the component location.

Shop Talk

If the problem occurs only at a certain engine temperature, be sure to check the engine speed sensor circuit while the engine is at that particular temperature.

Check for the correct air gap between the engine speed sensor and the flywheel. 019-042.

Refer to Troubleshooting Fault Code t05-121

Last Modified:  15-Jul-2010
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