Description of PID 45 – Cold Start (Grid Heater) Fault
The digital output for the grid heater relay is monitored for high/low state conformity. At the start of the preheating state and the starting state, and during the first two seconds of the preheating state, the intake air manifold temperature is measured to check if the cold start device (grid heater) works.
PID 45 indicates that a fault occurred during operation of the grid heater.
The diagnostic condition is typically:
- Open Circuit (045 03).
- Short to Ground (045 04).
The Vehicle Control Unit (DDEC-VCU) is the interface between the DDEC-VCU and the vehicle/equipment for engine control and manages the vehicle/equipment functions. See Figure "The DDEC-VCU" .
Figure 1. The DDEC-VCU
Wiring the Grid Heater
The output (pin 7 of the 21-pin connector) activates the grid heater control lamp. The output (pin 10 – of the 15-pin connector) activates the load relay for the grid heater. The digital input (pin 10 of the 12-pin connector) can be used for monitoring the load contacts of the load relay. If the output is shut off, the relay is switched to the supply voltage or to ground. See Figure "DDEC-VCU Grid Heater Wiring" .
Figure 2. DDEC-VCU Grid Heater Wiring
The grid heater, see Figure "Grid Heater" , is driven by the load relay switched to supply voltage. The installation of a fused high current, as well as the recommended monitoring of the load contact of the load relay, is the responsibility of the vehicle manufacturer.
Figure 3. Grid Heater
A sticking contact on the load relay can be monitored via input pin 10 of the 12-pin connector, but there is no automatic power cut off. If a load contact sticks, the grid heater control lamp will flash and the grid heater load circuit must be switched off manually.
Nominal power and resistance for the 12-volt grid heater is listed in Table "Nominal Power and Resistance" .
Nominal Power at 1000 °C (1832 °F)
1.9 kw ± 10%
Resistance at Rated Temperature
62 mΩ ± 10%
Note: The grid heater requires a 250 amp relay for 12-volt systems.
|MBE 900/4000 Troubleshooting Guide - 6SE422|
|Generated on 10-13-2008|