CAT 3126B Fault Code: 102-2 PID: Flash Code 25 SPN: 102 FMI: 2 Boost Pressure signal erratic

Posted by PerDiezel Solutions on January 12, 2026

The Engine Control Module (ECM) detects the following conditions:

•The difference between desired boost and actual boost is greater than 20 kPa (80 inch of H2O) for more than eight seconds.
•Desired boost is not ZERO.
•The ECM has been powered for at least two seconds.

This engine utilizes a wastegate control valve that is electronically controlled in order to precisely regulate the boost pressure. The Engine Control Module (ECM) monitors the signal from the boost pressure sensor in order to determine the boost pressure in the intake manifold. The ECM uses this information and other information that is related to the current power demand and the current engine operating conditions in order to determine the optimum position of the wastegate valve at the turbocharger.

The turbocharger’s wastegate valve regulates the amount of exhaust gas that is allowed to bypass the turbine wheel of the turbocharger. This allows the ECM to control the speed of the turbocharger and the boost pressure.

Probable Causes:

1) ECM Connection
2) Wastegate control solenoid (Can be replaced instead of the entire valve)
3) Harness between the ECM and the wastegate control solenoid
4) ECM Failure
5) Air inlet system restrictions or exhaust system restrictions
6) Drain orifice plugged

CAT 3126B Fault Code: 102-4 PID: Flash Code 25 SPN: 102 FMI: 4 Boost Pressure Short Circuit

CAT 3126B Fault Code: 102-3 PID: Flash Code 25 SPN: 102 FMI: 3 Boost Pressure Sensor Open Cicuit

CAT 3126B Fault Code: 100-04 PID: Flash Code 24 SPN: 100 FMI: 4 Oil Pressure voltage low

CAT 3126B Fault Code: 100-03 PID: Flash Code 24 SPN: 100 FMI: 3 Oil Pressure voltage high

CAT 3126B Fault Code: 232-04 PID: Flash Code 21 SPN: 620 FMI: 4 5 Volt Supply Below Normal

CAT 3126B Fault Code: 232-03 PID: Flash Code 21 SPN: 620 FMI: 3 5 Volt Supply Above Normal

WARNING!