Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCADILLAC1996ELDORADO V8-4.6L VIN 9REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONINITIAL INSPECTION AND DIAGNOSTIC OVERVIEWDIAGNOSING INTERMITTENTS
1996 Cadillac Eldorado V8-4.6L VIN 9
Diagnosing Intermittents
1996 Cadillac Eldorado V8-4.6L VIN 9SECTION Diagnosing Intermittents
Diagnosing Intermittents
Most tables have one result which reads FAULT NOT PRESENT. This means that the conditions that were present when the DTC set are no longer there. This does not mean that the problem is fixed, it simply means that the problem is intermittent. The problem was present but is not present now, and it is likely to return in the future so it should be diagnosed and repaired if at all possible. The only way to diagnose a problem that is not present is to gather information from the time when the DTC was set. This can be done in two ways; through snapshot data and driver observations.
Snapshot Data
Snapshot data whether Freeze Frame, Failure Records or scan tool snapshot, can be used to check data parameters to see if they fall within normal operating range. For example, a snapshot MAP parameter value of 100 while the engine was idling is not normal and would indicate that the MAP sensor voltage went high either due to an open in the 5 volt return or a short to voltage on the sensor signal circuit. Driver observations may give additional information about the system or area of the car that should be checked for an intermittent. For example, while diagnosing an intermittent DTC P0550, you find out the driver noticed that the SERVICE VEHICLE SOON message only comes on after an extended wide open throttle maneuver. This would lead you to check the wiring harness that carries the power steering pressure switch circuit underhood, because it is likely that powertrain movement (during WOT) is stretching the harness, causing an open circuit. This kind of information, while not airtight, may be very helpful in diagnosing intermittent conditions. Besides, it may be the only information you can get about a failure and the only chance to find the cause of an intermittent.
Most tables have one result which reads FAULT NOT PRESENT. This means that the conditions that were present when the DTC set are no longer there. This does not mean that the problem is fixed, it simply means that the problem is intermittent. The problem was present but is not present now, and it is likely to return in the future so it should be diagnosed and repaired if at all possible. The only way to diagnose a problem that is not present is to gather information from the time when the DTC was set. This can be done in two ways; through snapshot data and driver observations.
Snapshot Data
Snapshot data whether Freeze Frame, Failure Records or scan tool snapshot, can be used to check data parameters to see if they fall within normal operating range. For example, a snapshot MAP parameter value of 100 while the engine was idling is not normal and would indicate that the MAP sensor voltage went high either due to an open in the 5 volt return or a short to voltage on the sensor signal circuit. Driver observations may give additional information about the system or area of the car that should be checked for an intermittent. For example, while diagnosing an intermittent DTC P0550, you find out the driver noticed that the SERVICE VEHICLE SOON message only comes on after an extended wide open throttle maneuver. This would lead you to check the wiring harness that carries the power steering pressure switch circuit underhood, because it is likely that powertrain movement (during WOT) is stretching the harness, causing an open circuit. This kind of information, while not airtight, may be very helpful in diagnosing intermittent conditions. Besides, it may be the only information you can get about a failure and the only chance to find the cause of an intermittent.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.