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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15181
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Chevrolet Trailblazer LT: im a GM Tech too but im stumped

Customer Question

Hi im a GM Tech too but im stumped on this trailblazer I have in my shop
Submitted: 1 year ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 1 year ago.
HI there, Cam here. So persistent P1345. Let me pull up the manual, one moment.
Expert:  GM Tech (Cam) replied 1 year ago.
I have a GM bulletin thats worth looking at. Can you look and see if it applies.
Expert:  GM Tech (Cam) replied 1 year ago.
2003 Chevrolet TrailBlazer - 4WD | Bravada, Envoy, TrailBlazer VIN S/T Service Manual | Document ID:(###) ###-#### #PIP3659A: SES Light After Internal Engine Repairs Due to DTC P0016 or P1345 - keywords after cam correlation crank DTC induced previous replacement seal since spring timing valve - (Jan 4, 2006) Subject: SES Light After Internal Engine Repairs Due DTC P0016 or P1345 Models: 2004 Buick Rainier2002-2004 Chevrolet TrailBlazer2002-2004 GMC Envoy2002-2004 Oldsmobile Bravadawith 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. 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.
Customer: replied 1 year ago.

Well I have seen this bulletin. and I have replaced the timing chain components twice already. The actuator is brand new also. Timing marks all line up excatly. I thought maybe the actuator was defective so Im having the dealer warranty the part but its on backorder so there is no telling when I will get it.

Expert:  GM Tech (Cam) replied 1 year ago.
Ok, it is likely the cam gear itself, but lets touch on the other possible issues. Did you follow the manual in regards ***** ***** torque specs and such for all the cam gears, the harmonic balancer and is there any wobble or damage to the balancer itself?
Customer: replied 1 year ago.
I did follow torque spec for all gears and harmonic balancer appears to be fine. It is torqued to spec too and has the friction washer in place.
Expert:  GM Tech (Cam) replied 1 year ago.
Ok, then at this point I only can suggest one thing. Are the cam sensors rotated in their housing and in the correct position for each? The offset of the sensors I think is different and if they spin or move it can change the reading. IF that is good, then replace the actuator gear and see where that goes.
Customer: replied 1 year ago.
The cam and crank sensors are brand new and they only install 1 way.
Expert:  GM Tech (Cam) replied 1 year ago.
Ok I was expecting that, so then the cam gear is all I have left.

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