P0136,P0137, P0138, P0139,P0140
Symptom: CHECK ENGINE lamp (MIL) on. Any other diagnostic trouble codes, such
as misfiring and adaptation.
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P0136
,
P0137
,
P0138
,
P0139
,
P0140
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Rear heated oxygen sensor (oxygen sensor 2)
Fault symptoms
CHECK ENGINE lamp (MIL) on. Any other diagnostic trouble codes, such
as misfiring and adaptation.
Conditions
Sensor preheating active more than 200 seconds after starting
and
P0136 Sensor 2 voltage = 0 V for 200 seconds.
P0137 Shorting to ground for more than 0.12 seconds,
P0138 Shorting to battery positive (B+) for more than 0.12 seconds.
P0139 Sensor 1 voltage oscillates at too low a frequency.
P0140 No voltage from the sensor, open circuit for more than 100
seconds.
Diagnostic help
The performance of the oxygen sensor can be ascertained with an ISAT scan
tool.
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Select "READ
FUNCTIONS".
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Select "OXYGEN SENSOR".
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At full load the ISAT scan tool should show a reading that is > 0.7 V. At fuel
shut-off the ISAT scan tool should show a reading of about 0 V.
Note
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•
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If the reference ground or sensor
voltage of any of the oxygen sensors is shorted to battery negative (B-), diagnostic trouble
codes P0131 and P0137 could be generated simultaneously.
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•
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If the reference ground or sensor voltage of any of the oxygen sensors is shorted
to battery positive (B+), diagnostic trouble codes P0131 and P0138 could be generated
simultaneously.
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•
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If battery positive voltage (B+) is applied to any reference ground, the control
module could be damaged.
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If the preheating element of an oxygen sensor develops a fault the performance
of the sensor will deteriorate, particularly at idling speed. A diagnostic trouble code indicating a
defective sensor could then be generated. If a diagnostic trouble code for oxygen sensor
preheating is generated, it should be attended to first. Following this, the performance of the
oxygen sensor should be checked.
Check the wiring
Intermittent faults may occur as a result of temporary short circuits and breaks in the
wiring. Jiggle the wiring at several points and in different directions to ascertain whether the
wiring harness, including any connectors, is causing the trouble. Observe the multimeter,
ISAT scan tool or test lamp while doing this.
Diagnostic procedure
1. Check other Motronic 4.1 diagnostic trouble codes
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Use an ISAT scan tool to obtain
readouts of all diagnostic trouble codes.
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Any other diagnostic trouble codes?
Continue fault diagnosis for the relevant diagnostic trouble
code.
Continue with point 2.
2. Check the oxygen sensor's control module
input
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Unplug the oxygen sensor's
4-pin connector.
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Connect the ISAT Scan Tool.
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Turn the ignition switch to the ON position.
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Select "READ FUNCTIONS".
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Select "OXYGEN SENSOR".
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The ISAT scan tool should show a reading of about 0.45 V.
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Connect a jumper lead between
pins 3 and 4 in the oxygen sensor's connector.
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The ISAT scan tool should show a reading of 0 V.
Are all readings OK?
Change the oxygen sensor. Continue with point 4.
Check the relevant lead and repair or replace it if necessary. Continue with
point 3.
3. Check the wiring
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Check for continuity
between:
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If the ISAT scan tool shows the two diagnostic trouble codes P0137 and P0131,
the front heated oxygen sensor's ground connection should also be checked.
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Check for continuity
between:
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Is the wiring OK?
Continue with point 4.
Repair or replace the wiring. Continue with point 4.
4. Final check
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Clear the diagnostic trouble
code.
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Implementation of driving cycle:
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Evaluation of driving cycle:
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Does the ISAT scan tool read "NOT READY"?
Repeat the driving cycle.
Check whether the diagnostic trouble code has recurred.
Has the diagnostic trouble code recurred?
Continue as described in
.
The steps taken to rectify the fault were correct.
