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Mack fault codes

The reference covers 216 codes from the factory tables of Mack, grouped by control module (MID).

Engine (EECU)

CodeMeaning
M128-P100.3Engine Oil Pressure - High Voltage
M128-P100.4Engine Oil Pressure - Low Voltage/Open
M128-P102.3Boost Pressure - High Voltage
M128-P102.4Boost Pressure - Low Voltage/Open
M128-P103.8Turbocharger Speed - Abnormal Freq., PW or T
M128-P105.3Intake Manifold Temp. - High Voltage
M128-P105.4Intake Manifold Temp. - Low Voltage
M128-P105.5Intake Manifold Temp. - Current Low/Open
M128-P106.3Inlet Air Pressure - High Voltage
M128-P106.4Inlet Air Pressure - Low Voltage/Open
M128-P108.3Barometric Pressure - High Voltage
M128-P108.4Barometric Pressure - Low Voltage/Open
M128-P110.3Engine Coolant Temp. - High Voltage
M128-P110.4Engine Coolant Temp. - Low Voltage
M128-P110.5Engine Coolant Temp. - Current Low/Open
M128-P110.10Engine Coolant Temp. - Abnormal Rate of Change
M128-P111.3Coolant Level - High Voltage/Open
M128-P111.5Coolant Level Add Sensor - High Voltage/Open
M128-P158.4Switched Voltage - Low Voltage
M128-P171.3Ambient Temperature - High Voltage
M128-P171.4Ambient Temperature - Low Voltage
M128-P171.5Ambient Temperature - Current Low/Open
M128-P172.3Combustion Air Temperature - High Voltage
M128-P172.4Combustion Air Temperature - Low Voltage
M128-P172.5Combustion Air Temperature - Current Low/Open
M128-P174.3Fuel Temperature - High Voltage
M128-P174.4Fuel Temperature - Low Voltage
M128-P174.5Fuel Temperature - Current Low/Open
M128-P175.3Engine Oil Temperature - High Voltage
M128-P175.4Engine Oil Temperature - Low Voltage
M128-P175.5Engine Oil Temperature - Open
M128-P190.2Redundant Engine Speed Mon. - Timing and position do not agree
M128-P26.0Estimated % Fan Speed - Above Normal Op. Range
M128-P26.1Estimated % Fan Speed - Below Normal Op. Range
M128-P439.3Boost Pressure Extended - High Voltage
M128-P439.4Boost Pressure Extended - Low Voltage/Open
M128-P98.3Engine Oil Level - High Voltage
M128-P98.4Engine Oil Level - Low Voltage
M128-S1.2Injector #1 - Data Erratic
M128-S1.3Injector #1 - High Voltage
M128-S1.4Injector #1 - Low Voltage
M128-S1.8Injector #1 - Abnormal Freq., PW or T
M128-S147.7VGT Position Sensor - Mech. System Not Resp.
M128-S151.3System Diagnostic - Solenoid Boost Voltage - High Voltage
M128-S151.4System Diagnostic - Solenoid Boost Voltage - Low Voltage
M128-S2.2Injector #2 - Data Erratic
M128-S2.3Injector #2 - High Voltage
M128-S2.4Injector #2 - Low Voltage
M128-S2.8Injector #2 - Abnormal Freq., PW or T
M128-S21.2Engine Position Sensor - Data Erratic/Incorrect
M128-S21.8Engine Position Sensor - Abnormal Freq., PW or T
M128-S22.2Engine Timing Sensor - Data Erratic/Incorrect
M128-S22.8Engine Timing Sensor - Abnormal Freq., PW or T
M128-S231.8J1939 Link - Abnormal Freq., PW or T
M128-S233.12Fuel Control Module - Failed Device
M128-S236.2Power Relay - Data Erratic/Incorrect
M128-S250.8J1708/J1587 Link - Abnormal Freq., PW or T
M128-S254.4Power reset without key switch - Low Voltage
M128-S254.8All VECU Communications Lost - engine shutdown
M128-S26.3Aux. Output Device Driver - High Voltage
M128-S26.4Aux. Output Device Driver - Low Voltage
M128-S27.3Fan Clutch Output - High Voltage
M128-S27.4Fan Clutch Output - Low Voltage
M128-S3.2Injector #3 - Data Erratic
M128-S3.3Injector #3 - High Voltage
M128-S3.4Injector #3 - Low Voltage
M128-S3.8Injector #3 - Abnormal Freq., PW or T
M128-S32.2Wastegate Output - Data Erratic
M128-S32.5Wastegate Output - Open
M128-S32.7Wastegate Output - Mech. System Not Resp.
M128-S33.2Fan Clutch Output - Data Erratic
M128-S33.5Fan Clutch Output - Open
M128-S4.2Injector #4 - Data Erratic
M128-S4.3Injector #4 - High Voltage
M128-S4.4Injector #4 - Low Voltage
M128-S4.8Injector #4 - Abnormal Freq., PW or T
M128-S5.2Injector #5 - Data Erratic
M128-S5.3Injector #5 - High Voltage
M128-S5.4Injector #5 - Low Voltage
M128-S5.8Injector #5 - Abnormal Freq., PW or T
M128-S6.2Injector #6 - Data Erratic
M128-S6.3Injector #6 - High Voltage
M128-S6.4Injector #6 - Low Voltage
M128-S6.8Injector #6 - Abnormal Freq., PW or T
M128-S79.4Engine Brake Output #1 - Low Voltage
M128-S79.5Engine Brake Output #1 - High Voltage/Open
M128-S80.4Engine Brake Output #2 - Low Voltage
M128-S80.5Engine Brake Output #2 - High Voltage/Open
M128-S81.3Exhaust Brake Output - High Voltage
M128-S81.4Exhaust Brake Output - Low Voltage

Chassis/dash (VECU)

CodeMeaning
M142-P100.1Engine Oil Pressure - Engine Oil Press. Low
M142-P110.0Engine Coolant Temp. - Engine Coolant Temp. Hi
M142-P167.0Alternator Voltage - High Voltage
M142-P167.1Alternator Voltage - Low Voltage
M142-P168.1Battery Voltage - Low Voltage
M142-P170.3Cab Interior Temperature - High Voltage/Open
M142-P170.4Cab Interior Temperature - Low Voltage
M142-P173.0Exhaust Temperature - Exhaust Temperature High
M142-P173.3Exhaust Temperature - High Voltage
M142-P173.4Exhaust Temperature - Low Voltage
M142-P177.0Transmission Oil Temperature - Oil Temperature High
M142-P177.3Transmission Oil Temp. - High Voltage/Open
M142-P177.4Transmission Oil Temp. - Low Voltage
M142-P190.0Engine Speed - Engine Speed High
M142-P77.3F.R. Axle Oil Temperature - High Voltage/Open
M142-P77.4F.R. Axle Oil Temperature - Low Voltage
M142-P78.3R.R. Axle Oil Temperature - High Voltage/Open
M142-P78.4R.R. Axle Oil Temperature - Low Voltage
M142-P84.0Vehicle Speed - Vehicle Speed High
M142-P84.1Vehicle Speed - Below Normal
M142-P84.2Vehicle Speed - Data Invalid
M142-P84.3Vehicle Speed - High Voltage
M142-P84.4Vehicle Speed - Low Voltage
M142-P84.5Vehicle Speed - Open
M142-P84.8Vehicle Speed - Abnormal Freq., PW or T
M142-P84.11Vehicle Speed - Mode Not Identifiable
M142-P91.2Cummins Accel Pedal Position - Accel Pedal Invalid
M142-P91.3Accel. Pedal Position - High Voltage
M142-P91.4Accel. Pedal Position - Low Voltage/Open
M142-P91.7Cummins Idle Validation Switch - switch says idle, pedal not idle
M142-P91.14Cummins Idle Validation Switch - switch says not idle, pedal idle
M142-P96.3Fuel Level - High Voltage/Open
M142-P96.4Fuel Level - Low Voltage
M142-S10.3Aux. Output #1 - High Voltage
M142-S10.4Aux. Output #1 - Low Voltage
M142-S11.3Aux. Output #2 - High Voltage
M142-S11.4Aux. Output #2 - Low Voltage
M142-S12.3Spare Relay 3 - High Voltage
M142-S12.4Spare Relay 3 - Low Voltage
M142-S151.0CDS (Cust Def Stat) Fault - Above Normal
M142-S151.1CDS (Cust Def Stat) Fault - Below Normal
M142-S151.8CDS (Cust Def Stat) Fault - Abnormal Freq., PW or T
M142-S152.7Transmission Splitter Position - Mech. System Not Resp.
M142-S152.8Transmission Splitter Position - Abnormal Freq., PW or T
M142-S216.12Possible J1939 Link - Other ECU failure Affecting Operation
M142-S224.3Driver Alarm - High Voltage
M142-S224.4Driver Alarm - Low Voltage
M142-S231.8J1939 Link - Abnormal Freq., PW or T
M142-S231.14J1939 Link - Lost Contact with Tranny
M142-S232.3Vref Out of Range - High Voltage
M142-S232.4Vref Out of Range - Low Voltage
M142-S235.3Parking Brake - High Voltage
M142-S237.3Starter Input - High Voltage
M142-S238.3Shutdown Lamp - High Voltage
M142-S238.4Shutdown Lamp - Low Voltage
M142-S239.3Fault Lamp - High Voltage
M142-S239.4Fault Lamp - Low Voltage
M142-S242.3Spd Cntl Resume Switch - High Voltage
M142-S243.3Spd Cntl Set Switch - High Voltage
M142-S246.4Service Brake - Low Voltage
M142-S250.8J1708/J1587 Link - Abnormal Freq., PW or T
M142-S254.4Power reset without key switch - Low Voltage
M142-S254.12Exhaust Temp Reference - Failed Device
M142-S254.14Transport Protocol - Table programming failure
M142-S6.3Tachometer Output - High Voltage
M142-S6.4Tachometer Output - Low Voltage
M142-S7.3Speedometer Output - High Voltage
M142-S7.4Speedometer Output - Low Voltage

Engine, secondary module

CodeMeaning
M143-P100.3Engine Oil Pressure - High Voltage
M143-P100.4Engine Oil Pressure - Low Voltage/Open
M143-P102.3Boost Pressure - High Voltage
M143-P102.4Boost Pressure - Low Voltage/Open
M143-P105.3Intake Manifold Temp. - High Voltage
M143-P105.4Intake Manifold Temp. - Low Voltage
M143-P105.5Intake Manifold Temp. - Current Low/Open
M143-P106.3Inlet Air Pressure - High Voltage
M143-P106.4Inlet Air Pressure - Low Voltage/Open
M143-P110.3Engine Coolant Temp. - High Voltage
M143-P110.4Engine Coolant Temp. - Low Voltage
M143-P110.5Engine Coolant Temp. - Current Low/Open
M143-P111.3Coolant Level - High Voltage/Open
M143-P158.4Switched Voltage - Low Voltage
M143-P174.3Fuel Temperature - High Voltage
M143-P174.4Fuel Temperature - Low Voltage
M143-P174.5Fuel Temperature - Current Low/Open
M143-P98.3Engine Oil Level - High Voltage
M143-P98.4Engine Oil Level - Low Voltage
M143-S1.2Injector #1 - Data Erratic
M143-S1.3Injector #1 - High Voltage
M143-S1.4Injector #1 - Low Voltage
M143-S1.8Injector #1 - Abnormal Freq., PW or T
M143-S2.2Injector #2 - Data Erratic
M143-S2.3Injector #2 - High Voltage
M143-S2.4Injector #2 - Low Voltage
M143-S2.8Injector #2 - Abnormal Freq., PW or T
M143-S21.2Engine Position Sensor - Data Erratic/Incorrect
M143-S21.8Engine Position Sensor - Abnormal Freq., PW or T
M143-S22.2Engine Timing Sensor - Data Erratic/Incorrect
M143-S22.8Engine Timing Sensor - Abnormal Freq., PW or T
M143-S231.8J1939 Link - Abnormal Freq., PW or T
M143-S233.12Fuel Control Module - Failed Device
M143-S236.2Power Relay - Data Erratic/Incorrect
M143-S250.8J1708/J1587 Link - Abnormal Freq., PW or T
M143-S26.3Aux. Output Device Driver - High Voltage
M143-S26.4Aux. Output Device Driver - Low Voltage
M143-S27.3Fan Clutch Output - High Voltage
M143-S27.4Fan Clutch Output - Low Voltage
M143-S3.2Injector #3 - Data Erratic
M143-S3.3Injector #3 - High Voltage
M143-S3.4Injector #3 - Low Voltage
M143-S3.8Injector #3 - Abnormal Freq., PW or T
M143-S30.3Exhaust Brake Output - High Voltage
M143-S30.4Exhaust Brake Output - Low Voltage
M143-S33.2Fan Clutch Output - Data Erratic
M143-S4.2Injector #4 - Data Erratic
M143-S4.3Injector #4 - High Voltage
M143-S4.4Injector #4 - Low Voltage
M143-S4.8Injector #4 - Abnormal Freq., PW or T
M143-S5.2Injector #5 - Data Erratic
M143-S5.3Injector #5 - High Voltage
M143-S5.4Injector #5 - Low Voltage
M143-S5.8Injector #5 - Abnormal Freq., PW or T
M143-S6.2Injector #6 - Data Erratic
M143-S6.3Injector #6 - High Voltage
M143-S6.4Injector #6 - Low Voltage
M143-S6.8Injector #6 - Abnormal Freq., PW or T

How to read a code

A code has three parts: MID is which control unit reported it, PID/SID is which parameter or component is at fault, FMI is the type of fault (short circuit, open circuit, value out of range). On the scanner the code usually shows as MID-PID/SID-FMI, e.g. MID128 PID100 FMI4.

Know the code number? Type it into the search — or paste the whole list from the scanner and we will show which fault is the real one.