Cummins Fault Code 629

26/12/2025

Overview

CODE

REASON

EFFECT

Fault Code: 629
PID: S314
SPN: 1176
FMI: 1/18
LAMP: Amber
SRT:

The estimated differential pressure across the turbocharger is above the critical level.

Possible reduced engine performance.

Cummins Fault Code 629 — Engine Control Module (ECM)

Circuit Description

The ECM calculates a differential pressure across the turbocharger using the intake manifold pressure sensor and the crankcase pressure sensor.

Component Location

The intake manifold pressure sensor is located in the air intake horn. The crankcase pressure sensor is mounted to the crankcase breather filter housing.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the engine is running.

Conditions for Setting the Fault Codes

The Engine Control Module (ECM) detected the calculated differential pressure across the turbocharger was greater than a threshold.

Action Taken When the Fault Code is Active

The ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code

To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
The fault code status displayed by the recommended Cummins electronic service tool or equivalent will change to INACTIVE immediately after the diagnostic runs and passes.
The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
The “Reset All Faults” command in the recommended Cummins electronic service tool or equivalent can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.