Cummins ISB CM550 (1990-94) Fault Code: 115VP30 PID: 190 SPN: 190 FMI: 2 Engine Speed Sensor (ESS) Circuit

Posted by PerDiezel Solutions on January 16, 2026

Circuit Description
The engine speed sensor provides engine speed information to the engine control module (ECM). The sensor must be powered up by (+) 5 VDC to operate. The sensor generates its signals by
sensing the movement of target teeth machined into a tone wheel that is mounted to the crankshaft. The tone wheel has 35 teeth and a gap where the 36th tooth would be placed. This missing tooth indicates cylinder 1 and 6 are at top dead center.

Component Location
The combination sensor is located in the back of the gear housing behind the injection pump on QSB
engines with the Bosch VP30 fuel system.

Shop Talk
This fault code will also cause a fuel derate. This could be the cause of a low-power complaint. Also, this fault code can cause starting problems in cold weather.
QSB engines with the Bosch VP30 fuel system use only an engine speed sensor located in the
gear housing below the injection pump that reads off a tone wheel bolted to the camshaft gear. This is a combination sensor that provides both speed and position.

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Cummins ISB4.5 CM2150 Fault Code: 4769 PID: SPN: 1761 FMI: 11 Aftertreatment 1 Diesel Exhaust Fluid Tank Level Sensor – Root Cause Not Known.

Cummins ISB4.5 CM2150 Fault Code: 4739 PID: SPN: 1761 FMI: 11 Aftertreatment 1 Diesel Exhaust Fluid Tank Level Sensor – Root Cause Not Known.

Cummins ISB4.5 CM2150 Fault Code: 4737 PID: SPN: 3031 FMI: 11 Aftertreatment 1 Diesel Exhaust Fluid Tank Temperature – Root Cause Not Known.

Cummins ISB4.5 CM2150 Fault Code: 4732 PID: SPN: 1761 FMI: 13 Aftertreatment Diesel Exhaust Fluid Tank Level Sensor – Out of Calibration.

WARNING!