What is the CPC Module Freightliner?

As e-commerce grows exponentially, logistics are critical to homes and businesses worldwide. Yet, the success of a logistics process depends on numerous factors, which all come down to the timely delivery of goods.

Any driver’s worst nightmare is a truck that breaks down in the middle of nowhere. In the middle of the night. In the middle of a storm. Even without the extreme circumstances, a breakdown is still a huge inconvenience that requires immediate attention to stay on track. This means that the truck and all its components must be of top-notch quality and capable of handling long distances without qualms. In the mighty Freightliner Cascadia, this includes the handy CPC4.

What is the CPC module?

Has your truck suddenly suffered engine trouble and sent out a J1939 or J1587 that leaves you wondering what on earth is wrong? Random troubleshooting could easily have you take apart the entire vehicle looking for the component that needs attention.

This little bugger is the Common Powertrain Controller that links the MCM and the truck for numerous functions, the chief being engine control. The OEM mounts the CPC in an enclosed, protected environment, so it is away from other electrical components in the truck.

The CPC stores data including idle speed, maximum running speed, speed limitations, and customer-programmable parameters. It also receives data from the processor, including accelerator pedal position, switches and sensors, and other electronic control units like air compressor controls.

The Freightliner Cascadia cpc4 has three 18-pin connectors and one 21-pin connector, which feed data into the system for various functions.

Connector 1:

Pin Signal Type Function
1 Digital Input_FLEX_01  Multiple Applications
2 Digital Input_FLEX_02 Park Brake Interlock
3 Digital Input_SFP_05 Idle Validation Switch 2 (throttle active)
4 Digital Output_LP_LS_02 Throttle Position Sensor Ground
5 Digital Output_LP_LS_01 DPF Regeneration Lamp
6 Digital Input_SFP_06 Idle Validation Switch 1 (idle active)
7 SFP_08 Throttle Position Sensor
8 SFP_07 Throttle Position Sensor Supply
9 PWM_FPO_02 Tachometer
10 Digital Input_FLEX_20 Multiple Applications
11 Digital Input_FLEX_08 Limiter 0
12 Digital Input_FLEX_03 Set / Coast Enable
13 Digital Output_LP_FLEX_01 MIL Lamp
14 Digital Input_FLEX_04 Cruise Control Enable
15 Digital Input_FLEX_05 Stop Engine Override
16 Digital Input_FLEX_06 Resume / Accel Enable
17 Digital Input_FLEX_07 Multiple Applications
18 SFP_01 Run Start


Connector 2:

Pin Signal Type Function
1 Battery (+) PSU (KL_30) Main Battery +12 V
2 Battery (-) PSU (KL_31) Main Battery Ground
3 Battery (+) Switched PSU Ignition
4 K_DIAG_C K-line
5 J 1708_A Not Used
6 J 1708_B  Not Used
7 Digital Input_FLEX_15 Multiple Applications
8 Digital Input_FLEX_16 Multiple Applications
9 Digital Input_FLEX_09 Multiple Applications
10 Digital Output_LP_FLEX_03 Amber Warning Lamp
11 Digital Input_FLEX_10 Limiter 1
12 Digital Input_FLEX_11 A/C Status
13 Digital Input_FLEX_12 Multiple Applications
14 Digital Input_FLEX_13 Multiple Applications
15 Digital Input_FLEX_14 Multiple Applications
16 VCAN_L_C J1939 (-)
17 VCAN_GND_C J1939 Shield
18 VCAN_H_C J1939 (+)


Connector 3:

Pin Signal Type Function
1 Analog_In_01 Multiple Applications
2 Analog_GND Sensor Return
3 Analog__SUP_5V Sensor Supply
4 Analog_In_02  PTO
5 Analog_Out_01 Multiple Applications
6 Analog_Out_02 Multiple Applications
7 Digital Output_HP_HS_01 Multiple Applications
8 Digital Output_HP_HS_02 Multiple Applications
9 Digital Output_HP_LS_01 Multiple Applications
10 Digital Output_LP_FLEX_02 DEF Low Lamp
11 SFP_14 Low Coolant Level Sensor
12 Digital Output_LP_FLEX_04 Multiple Applications
13 SFP_09 Vehicle Speed (+)
14 SF_VGND Vehicle Speed (-)
15 Analog_In_SFP_13 Ambient Air Temp Sensor
16 Digital Output_LP_FLEX_05 Red Stop Lamp
17 Digital Output_HP_FLEX_02 Multiple Applications
18 Digital Input_SFP_02 Multiple Applications
19 PTCAN_L 5V Powertrain CAN (-)
20 PTCAN_GND 5V Powertrain CAN Shield
21 PTCAN_H 5V Powertrain CAN (+)


Connector 4:

Pin Signal Type Function
1 C_ECAN_L Not Used
2 C_ECAN_GND Not Used
3 C_ECAN_H Not Used
4 Digital Input_SFP_11 Not Used
5 Digital Input_SFP_12 Not Used
6 Digital Output_LP_FLEX_06 Wait to Start Lamp
7 Digital Output_HP_LS_02 High Exhaust Temperature Lamp
8 Digital Input_FLEX_E1 Multiple Applications
9 Digital Output_HP_FLEX_01 Multiple Applications
10  Digital Output_HP_HS_04 Multiple Applications
11 Frequency_SFP_10 Not Used
12 PWM_FPO_01 Multiple Applications
13 Digital Input__FLEX_19  DPF Inhibit Switch
14 Digital Input_SFP_03 Not Used
15 Digital Input_SFP_04 Not Used
16 Digital Input_FLEX_17 Multiple Applications
17 Digital Input_FLEX_21 DPF Regeneration Switch
18 Digital Input_FLEX_18 Multiple Applications

When mounting the CPC, remember to plug in the connectors facing downwards. Moreover, the VIH should be at least 3 feet far from other truck electrical systems. Finally, the wires should not run parallel to the VIH to avoid coupling electromagnetic energy into the VIH.

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