"Dear Ghibli II owners,
I am often asked about the CHECK ENGINE light.
"Dear Sir,
I own a Ghibli II, model 1994. I have the check engine sign on. Do you know how to check what is the problem? Can you help me?"
The CHECK ENGINE light usually comes on when there is a fault in one or more of the following:
ENGINE SENSOR
This error may be caused by a fault in the sensor, by an air gap lower or higher than the permitted values, by a missing pulley tooth or by wiring problems.
The sensor can be verified by measuring resistance directly on the sensor, or between terminals 3 and 4 of the 35-way connector of the bank's engine control unit, in the latter case also verifying at the same time continuity of the wiring. If it is working, the sensor should give a reading of between 600 and 700 Ohm. If the signal is missing, the bank
stops immediately.
CAMSHAFT SENSOR
This error may be caused by a defect of the sensor, by an air gap lower or higher than the permitted values, by a missing pulley tooth or by wiring problems.
The sensor can be verified by measuring resistance directly on the sensor, or between terminals 5 and 23 of the 35-
way connector of the bank's engine control unit, in the latter case also verifying at the same time continuity of the wiring. If it is working, the sensor should give a reading of between 600 and 700 Ohm. If the signal is missing during
starting, no ignition or injection occurs. If the sensor breaks during operation, the engine continues to work normally
but the Check Engine lamp lights up.
SEQUENCE
Determined by incorrect sequence of the signal pattern. Incorrect sequence may be caused by a faulty sensor, an incorrect air gap value, a missing pulley tooth, wiring problems or by one or more camshafts out of phase.
MIXTURE STRENGTH
The Mixture Strength error is the most complicated one to fix as it may be caused by numerous components. such as the Water Temperature Sensor, Absolute Pressure Sensor, Air Temperature Sensor. As a result, of the components concerned have to be checked out one by one.
In the case of the Absolute Pressure Sensor, the pneumatic connection to the sensor also has to be checked as a
leak involves an incorrect pressure reading, with resultant incorrect reference on the map and hence an inappropriate air/fuel ratio.
Troubleshooting should therefore begin with the absolute pressure sensor as oil or dirt may have deposited on the
sensor diaphragm during car running and be the cause of a false pressure reading. If the absolute pressure sensor
is not working property, the car will have difficulty starting or may even run irregularly without signalling the error
code. This pattern of behaviour always occurs within a given interval of engine revs.
If the problem lies with the Water Temperature Sensor, an important indicator of this is difficulty in starting when the
engine is hot. In both cases, black smoke will issue from the exhaust after starting.
AIR TEMPERATURE SENSOR
The control unit has identified a short circuit or open circuit of the sensor. Replace the sensor and/or check the wiring.
KNOCK SENSOR
The control unit has identified a short circuit or open circuit of the sensor but only above 4,000 rpm.
Therefore if the sensor is broken with the engine operating at less than 4,000 revs/min, no error code will be signalled.
Replace the sensor and/or check the wiring.
WATER TEMPERATURE SENSOR
The control unit has identified a short circuit or open circuit of the sensor.
Replace the sensor and/or check the wiring (see also the description of the Mixture Strength error).
LAMBDA SENSOR
The Lambda Sensor error may be caused by incorrect operation of the sensor due to a short circuit or open circuit or a defect of the control unit not driving the sensor correctly anymore, maintaining a mixture that is always rich or poor.
ABSOLUTE PRESSURE SENSOR
The control unit has identified a short circuit or open circuit of the sensor. The sensor operates with a voltage of 0 - 5 Volts, which is supplied by the engine control unit.
Replace the sensor and/or verify the wiring (see also the description of the Mixture Strength error).
THROTTLE POSITION SENSOR
Throttle Position Sensor errors may be caused by short circuit, open circuit, no potentiometer power voltage (+5 Volts from the engine control unit), or output voltage value of less than 100 mVolts.
If there is a problem with the sensor, the error will be signalled on both control units. As there is only one Check
Engine lamp.
CONTROL UNIT OR EPROM ERROR
Replace the control unit. |
PLEASE NOTE:
If your CHECK ENGINE light comes on and STAYS ON, it could be nothing, but on the other hand it could be SERIOUS!
A visit to your nearest Official Maserati dealer or a recognised Maserati specialist AS SOON AS POSSIBLE is your best option.
They can carry out the relevant test using their diagnostic test equipment, and will be able to pinpoint your problem.
DON'T TAKE ANY CHANCES, THESE ARE VERY EXPENSIVE ENGINES TO REBUILD!!!! |