| Subject: | SES Light After Internal Engine Repairs Due DTC P0016 or P1345 |
| Models: | 2004 Buick Rainier |
| 2002-2004 Chevrolet TrailBlazer |
| 2002-2004 Oldsmobile Bravada |
| with 4.2L Engine (VIN S - RPO LL8) |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Depending on the model year, a P0016 or P1345 may be encountered after internal engine repairs that required resetting of the timing chain tensioner or removal and installation of the exhaust camshaft actuator sprocket. This may be the result of a mistimed
engine or damaged exhaust camshaft actuator.
Recommendation/Instructions:
If this concern is encountered and the SI diagnostics do not isolate the cause, review the following information and inspect for a damaged exhaust camshaft actuator or mistimed engine as necessary:
| • | The spline style exhaust camshaft actuator used on 2004 model year and earlier 4.2L engines is designed to operate between 25 degrees of retard and 0 degrees (full advance/rest/clockwise position). There is a stop tab inside of the camshaft actuator
that prevents the exhaust cam from advancing beyond the rest position under normal operating conditions. This tab can bend if the exhaust cam/actuator is forced to rotate beyond the rest position (full advance/full clockwise) during internal engine repairs.
If this occurs, it may be noted that the reluctor portion of the actuator is a few degrees more advanced (clockwise) than a known good one. With the actuator sprocket in place and the #1 piston at top dead center, it may be noted that the rear cam flat of
the exhaust cam is not flat when compared with the rear cam flat of the intake cam. Upon further inspection, it may also be noted that the word Delphi that is on the cam reluctor portion of the actuator is slightly rotated toward the driver side even though
the intake cam flat is flat. If this is suspected to be the cause of this concern, it will be necessary to replace the exhaust camshaft actuator again, taking care not to damage it upon reassembly. As mentioned in SI, do not force the camshaft actuator to
rotate clockwise upon assembly. If it does not move easily, it is already fully advanced. New camshaft actuators are already packaged in the fully advanced (clockwise) position. This type of damage should not occur on 2005 model year and newer 4.2L engines
because they are equipped with a vane style exhaust camshaft actuator, which is designed differently than the spline style actuator.
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| • | If the timing chain tensioner had to be reset, this concern could be the result of incorrect cam to crank timing. As the timing chain tensioner is released, chain slack between the crankshaft and tensioner is eliminated. As the slack is eliminated,
it is very easy for the timing chain to shift one tooth at the crankshaft sprocket without being noticed by the technician. If this occurs, it is unlikely to isolate the incorrect cam to crank timing without removing the front cover. When properly timed, the
timing marks should line up as shown below once every 14 crankshaft revolutions with the #1 piston at top dead center. If all 3 of these timing marks never line up at the same time, retime the engine by following SI procedures.
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Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
