ELECTRICAL AND ECU
Component Tests
12/05
BY Service Manual
12-17
© 2009 Yanmar Marine International
Glow Plug / Control Unit
The System
The glow plug control system consists of the
following components:
•ECU
• Electronic glow plug control unit
•Glow plugs
• Bit-serial data (BSD) interface and electrical
cables
The following information is important to
understand the glow plug control:
• Glow plugs are designed for operating voltage
between 5.3 and 7.8 volts
• Glow plugs are fast-start type
• Glow plug regulation is pulse-width modulated
• The electronic glow plug control unit replaces the
more commonly used relay
• The implementation of a function for emergency
cases
• Each circuit can be individually diagnosed
Function
The glow plug control unit communicates with the
ECU via the bit-serial data interface. The heating
output is calculated by the ECU according to the
coolant temperature and the system voltage.
Engine speed and injection rate affect the rate at
which the glow plugs are switched on and off.
Preheating
When the coolant temperature is above 25°C
(77°F), the unit will operate for 0.5 seconds. As
temperatures decrease below 25°C (77°F), the
on-time will increase up to a maximum of 2.7
seconds, depending on temperature.
If the key switch is turned to ON but the engine is
not started immediately, the controller will continue
to implement the glowing process for 10 seconds.
Post-Heating
Once the engine is started and the coolant
temperature increases above 30°C (86°F), post
heating will occur to improve idle and reduce
emissions.
Results of Component Failure
Component failure results in:
• P0671 - cylinder 1 glow plug circuit - not
connected / short circuit
• P0672 - cylinder 2 glow plug circuit - not
connected / short circuit
• P0673 - cylinder 3 glow plug circuit - not
connected / short circuit
• P0674 - cylinder 4 glow plug circuit - not
connected / short circuit
• P0675 - cylinder 5 glow plug circuit - not
connected / short circuit
• P0676 - cylinder 6 glow plug circuit - not
connected / short circuit
• P0670 - Glow control unit - component failure /
short circuit / over-current
• P0380 - Glow control relay actuator - not
connected / short circuit
Test Values
Glow plug resistance at 20°C (68°F): 0.5 ohm
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