Troubleshooting

i06704120
Glow Plug Starting Aid - Test
This procedure covers the following diagnostic
codes:
Table 68
Diagnostic Trouble Codes for the Glow Plug Start Aid Circuit
J1939
Code
Description
Notes
676-5 Engine Glow Plug Relay : Current Below
Normal
The Electronic Control Module (ECM) detects a low current condition in the control cir-
cuit for the Glow plug Control Unit (GCU) for at least 0.7 seconds.
The warning lamp will come on.
676-6 Engine Glow Plug Relay : Current Above
Normal
The ECM detects a high current condition in the control circuit for the GCU for at least
0.2 seconds.
The ECM will attempt to activate the glow plug control unit for a further five attempts
after the diagnostic code becomes active.
The warning lamp will come on.
676-19 Engine Glow Plug Relay : Data Error The ECM detects one of the following conditions:
The diagnostic signal from the GCU indicates that there is an error in the GCU.
OR
The diagnostic signal from the GCU is invalid.
The warning lamp will come on.
5324-7 Engine Glow Plug 1 : Not Responding
Properly
The ECM detects the following conditions:
The diagnostic signal from the GCU indicates that there is a short in the circuit for the
glow plug for cylinder number 1.
5325-7 Engine Glow Plug 2 : Not Responding
Properly
The ECM detects the following conditions:
The diagnostic signal from the GCU indicates that there is a short in the circuit for the
glow plug for cylinder number 2.
5326-7 Engine Glow Plug 3 : Not Responding
Properly
The ECM detects the following conditions:
The diagnostic signal from the GCU indicates that there is a short in the circuit for the
glow plug for cylinder number 3.
5327-7 Engine Glow Plug 4 : Not Responding
Properly
The ECM detects the following conditions:
The diagnostic signal from the GCU indicates that there is a short in the circuit for the
glow plug for cylinder number 4.
The following background information is related
to this procedure:
The starting aid is used to improve the engine
starting when the engine is cold. With the keyswitch
in the ON position, the Electronic Control Module
(ECM) will monitor the coolant temperature and the
engine air inlet temperature to decide if the glow
plugs need to be switched ON. If the glow plugs are
required, then the ECM will activate the glow plug
control unit for a controlled period. While the glow
plug control unit is activated, the glow plug control
unit will supply power to the glow plugs.
Glow plugs are used for temperatures that are below
5° C (41° F).
The GCU transmits a diagnostic signal back to the
engine ECM. If the GCU detects a fault for one of the
glow plugs, a diagnostic code will become active for
that glow plug.
134 UENR0612-07
Circuit Tests
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