Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
System overview: Signals
The chart below summarizes input and output signals to and from the combustion preheater module. The signal types are divided into directly connected signals, serial communication and Control area network (CAN) communication. The illustration below displays the same information with the Volvo part numbers.
| Input signals | Output signals |
| Directly connected: | Directly connected: (power supply unless otherwise stated) |
| Flame sensor (photo sensor) | Fuel pump |
| Coolant temperature sensor (NTC resistor) | Water pump |
| Fan motor reading (Electromotive force supply) | Glow plugs (pulse width modulation (PWM)) |
| Combustion fan (pulse width modulation (PWM)) | |
| (The supply relay must be active before the components can be activated) | |
| Via serial communication: | Via serial communication: (The heater communicates with the central electronic module via serial communication) |
| Start/stop signal for the heater | Heater operating status |
| Coolant temperature | |
| Diagnostic trouble code (DTC) list | |
| Heater running time | |
| Via Control Area Network (CAN): | Via CAN communication: (The heater communicates with the rest of the Control area network (CAN) via the central electronic module) |
| ECM, 4/46 | Driver Information Module, 5/1 |
| Driver Information Module, 5/1 | Steering wheel module, 3/130 |
| Steering wheel module, 3/130 | Climate control module, 3/112 |
| Climate control module, 3/112 | Accessory Electronic Module, 4/78 |
| Rear electrical module, 4/58 | |
| Driver's door module/passenger door module, 3/126-127 | |
| Accessory Electronic Module, 4/78 | |
| SRS, 4/9 |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.