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.
Signal Specification
All values given below are between the respective terminal in column 1 and terminal #3 (power ground) unless otherwise stated in brackets after the entry. Control module terminals #1-#16 correspond to terminals #1-#16 on the breakout box.
| U= | DC voltage in volts (V) | UAC = | AC voltage in volts (V) |
| Ubat = | Battery voltage (V) | f = | Frequency in Hertz (Hz) |
| Ulow = | Voltage approximately 0 V | % duty = | Duty cycle (pulse ratio) as a percentage (%) |
| t = | Time in milliseconds (ms) | - | - |
| Terminal | Signal type | Ignition on | Engine idling | Other |
| #1 | Glow plug signal | Glow plug off: U=Ulow Glow plug on: Pulse ratio (% duty) > 0% |
Pulse ratio (% duty) increases with glow plug intensity. | |
| #2 | - | - | - | |
| #3 | Power ground (Measured to the battery negative terminal) |
U low | - | |
| #4 | Signal ground, engine coolant temperature sensor and flame sensor | U low | - | |
| #5 | - | - | - | |
| #6 | Communication cable for the central electrical module (CEM) | - | Digital signal | - |
| #7 | - | - | - | - |
| #8 | Flame sensor signal | Flame not lit: U≈5 V Flame lit: U<1.5 V |
- | |
| #9 | 30-supply (Power supply from battery) | U bat | - | |
| #10 | Combustion fan control signal | Combustion fan off and power supply off: U low Combustion fan off and power supply on: U bat Fan on: Pulse ratio (% duty) > 0% |
The pulse ratio (% duty) increases with fan speed. | |
| #11 Model year -2001 |
Power supply, combustion fan, fuel pump (FP) and water pump | Power supply off: U low Power supply on: U bat |
- | |
| #11 Model year 2002- |
Power supply, combustion fan and water pump | Power supply off: U low Power supply on: U bat |
- | |
| #12 | Water pump control signal | Water pump off and power supply off: U low Water pump off and power supply on: U bat Water pump on and power supply on: U low |
- | |
| #13 | Fuel pump control signal | Fuel pump off: f=0 Hz Fuel pump on: f>0 Hz |
The frequency increases with pump speed | |
| #14 | - | - | - | |
| #15 | Extended X-supply | U bat | U bat | - |
| #16 | Coolant temperature sensor signal | +20°C: U ≈ 3.5 V +75°C= 2.02 V +90°C= 0.78 V |
The voltage decreases with increasing temperature | |
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
No obligation. See pricing before you book.