P1391
Read the instructions below then
start the fault diagnostic procedure.
Symptom: CHECK ENGINE.
Uneven running and misfiring.
Cylinder 1 Misfire Detected. Catalyst Damaging. Fuel Level Low.
Fault symptoms
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Uneven running and misfiring.
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On-Board Diagnostics
Type of diagnosis:
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Continuous. However, it is interrupted once the fault criteria have been fulfilled and does not restart until the next driving cycle.
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Enable criteria:
(Conditions that must be fulfilled for diagnostics to be performed.)
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Global conditions for this diagnostic trouble code: Atmospheric pressure must exceed 78 kPa, coolant and intake air temperatures must exceed -7°C.
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Engine running. Fuel level below 4 litres. Main relay voltage exceeding 10V. Combustion signals from the ignition discharge module are registered. The number of missing combustion signals is accumulated for each cylinder every 200th engine revolution. The total number of permitted misfires during 200 engine revolutions is specified in a load and speed-dependent matrix.
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Fault criteria:
(When enable criteria have been fulfilled, diagnostics will check if the fault criteria have been fulfilled.)
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The number of missing combustions exceeds the number of permitted misfires.
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Dependents:
(Once fault criteria have been fulfilled, a number of other diagnostics must report OK before the diagnostic trouble code can finally be generated.)
System reaction to a fault:
(Once the fault criteria have been fulfilled, certain measures will sometimes be taken.)
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Under heavy engine loads, closed loop is blocked while misfiring occurs.
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OK report:
(This diagnosis may be included as a dependent to another diagnosis and must therefore report OK even if it is continuous. The OK report is also used in fault handling to count down the fault counter.)
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On condition that the fault criteria have not been fulfilled during the driving cycle, an OK report is issued after the ignition is turned off and before the engine has stopped. Two types of OK report can be issued:
Type 1: If a diagnostic trouble code is already stored for the diagnosis and the same operating conditions have occurred (coolant temperature above or below 71°C, engine speed +/-375 rpm and load +/-10%).
Type 2: If there is no diagnostic trouble code stored for the diagnosis or the same operating conditions have not occurred.
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Fault handling:
(Refer to section “Fault diagnosis, general” for more information.)
Diagnostic help
If other diagnostic trouble codes are generated, check whether to start fault diagnosis with any of them. Drive the car in the load and speed-range indicated by the freeze frame. If the engine does not misfire, it can be assumed that the diagnostic trouble code was generated by a low fuel level. Drive the car so that the catalyst diagnosis is performed. Change the catalytic converter if necessary.
If the engine misfires during test driving then conduct a general check of the connectors and hoses and then a thorough check of the compression, ignition timing and fuel system.
Diagnostic tool functions related to this fault:
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Diagnostic status for the diagnosis.
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Misfire counter for the cylinder concerned.
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Activation and zeroing of the misfire counter.
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Activation of ignition trigger for the cylinder in question.
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Activation of the injector test for the cylinder in question.
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Refer also to the description of activations under ”Fault diagnosis, general” for more information.
Check the wiring
Jiggle the wiring harness at several points and in different directions to check if there are intermittent breaks and short-circuits in the leads. Observe the multimeter, test lamp or diagnostic instrument during the test.
