Engine Timing Issue?

SES light indicates engine timing is off. Vehicle runs fine. Mechanic is telling me I need to replace the distributor and a sensor of some kind that is associated with it. Also saying the timing chain might need replacement. Seems like I would be seeing some performance issues if that were the case. Vehicle is 99 k1500 with 125k highway miles. Any opinions?

SES light indicates engine timing is off. Vehicle runs fine. Mechanic is telling me I need to replace the distributor and a sensor of some kind that is associated with it. Also saying the timing chain might need replacement. Seems like I would be seeing some performance issues if that were the case. Vehicle is 99 k1500 with 125k highway miles. Any opinions?

Has the distibutor been removed recently for any reason?
Is the code P1345?
If the dist. has not been out, I would pull it and look closely at the drive gear..it may be worn.

The code is P1345. The other major work done on the engine recently was replacing the intake gasket. Would that have involved removing the distributor? Come to think of it, the SES light did come on while driving it home after that work was done!

Yes, you have to remove the distibutor to do an intake.
What has happened is the distibutor is out of time, therefore the CKP and CMP are not referenced right.
To bring the CKP/CMP back to its proper relationship, you will need a bidirectional scan tool that reads CMP offset.
Offset should be 0 at 2000 rpm
You cannot time one of these engines with a timing light