P1251,1252
Symptom: The CHECK ENGINE lamp does not light up when the ignition switch is
turned to the Drive position.
CHECK ENGINE lamp (MIL), output from control module
low/high
or shorting to ground/batt+
Fault symptom
The CHECK ENGINE lamp does not light up when the ignition switch is
turned to the Drive position.
Condition
Shorting to ground/batt+ in the circuit to pin 22
1.
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Activate the ISAT command
"CHECK ENGINE" in the "ACTIVATE"
menu. If the lamp cannot be activated or does not light up when the
ignition switch is in the drive position, continue with point 2.
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2.
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With the ignition switched off, connect a BOB to the MOTRONIC
control module.
With the ignition switch in the Drive position, check
whether the CHECK ENGINE lamp lights up when a jumper lead is connected across pins 14
and 22.
If it does not, check whether the lamp receives any current (see Service Manual
3:5)
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Also check the lead and connector for continuity
between pin 22 of the control module and the lamp.
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3.
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The CHECK ENGINE lamp should light up when the control module
grounds pin 22 if a diagnostic trouble code is generated or always when
the ignition is switched on.
Take a voltage reading across pins 37 and 22 on the
BOB. Battery voltage should be present when the ignition is switched
on.
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4.
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If no faults can be detected after carrying out the above diagnostic
procedure, clear all trouble codes and drive the car on the road to
check whether any trouble codes are generated afresh. If they are, turn
to
for further diagnostic instructions.
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