Hello & Welcome to JA,
This problem is an incorrect reading from the camshaft /crankshaft sensors. The fault can be a camshaft sensor,crankshaft sensor or a reluctor ring on the crankshaft that has moved. I am sending some info to help you.
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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
The dealer may have to remove and reinstall timing chains on the 3.6 LY7 or have misfires upon completion of the repair. This may be of assistance.
Note: When removing the front cover be sure to remove the belt tensioner and all the bolts. Damage may occur to the block if this procedure is not followed.
Note: When removing the front cover do not pry against or strike the cam actuators. This will cause damage to the reluctor or actuator.
Note: BE SURE to note the orientation of the injector wiring harness. The harness with connector should come out on the front side of the engine. It can be installed backwards and will cause misfires and/or fuel trim DTCs.
Here are some pictures that may assist when timing this engine.
Start with engine in stage one position with tool EN 46105-1 or EN 48383-1 on the left bank or bank 2. The circular timing marks on the camshafts should be aligned as shown.
The intermediate gear for the left secondary chain is shown below. The painted link should be visible through the hole.
Stage one primary chain alignment for the crankshaft and the left intermediate gear are shown below. The intermediate gear has a triangular shaped timing mark that aligns with the painted link and the crankshaft has a dot to dot alignment.
The right intermediate gear has a triangular mark that aligns with the painted link.
Remove EN 46105-1 or 48383-1 from the left bank. The engine will need to be rotated 115 degrees clockwise for stage two timing. The crankshaft marks should align dot to dot. Tool EN 46105-2 should fit easily on the rear of the cams on the left bank of the engine.
EN 48383-3 should be installed on the right bank or bank one. The triangular marks should be aligned as shown.
The painted link on the right intermediate shaft should be aligned with the hole in the rear gear.
The left camshafts will be aligned as shown when in Stage two timing position.
If there are any concerns in identifying the correct location for the camshafts check the number stamped in the rear of the camshaft
RI is right intake, RE is right exhaust, LI is left intake and LE is left exhaust.
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.