CAT 3126B Fault Code: 108-03 PID: Flash Code 26 SPN: 108 FMI: 3 Barometric Pressure voltage high

Posted by PerDiezel Solutions on January 12, 2026

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

•The signal voltage from the atmospheric pressure sensor is greater than 4.9 VDC for more than 30 seconds.
•The ECM has been powered for at least two seconds.

The Engine Control Module (ECM) continuously creates a pull-up voltage on the signal wire for each sensor. The ECM uses this pull-up voltage in order to detect a problem in the signal circuit. When the ECM detects voltage that is above a threshold on the signal wire, the ECM activates a -3 diagnostic code. When the ECM detects voltage that is below a threshold on the signal wire, the ECM activates a -4 diagnostic code.

Note: When you check for a diagnostic code, be sure to wait at least 30 seconds.

The most likely cause of a code is a problem with an electrical connector or wiring. The least likely cause of a code is the ECM.

The following sensors are included in this code:

Fuel pressure sensor
Injection actuation pressure sensor
Barometric pressure sensor
Boost pressure sensor
Engine oil pressure sensor

Probable Causes:

1) ECM Connection
2) Sensor failure
3) Sensor harness/connector
4) ECM Failure

CAT 3126B Fault Code: 102-7 PID: Flash Code 25 SPN: 102 FMI: 7 Boost Pressure not responding

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

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

WARNING!