My car has these codes: 16-low resolution pulse failure, 42-EST grounded, 44-left oxygen sensor lean, 52-ECM Prom Failure. My service engine light comes on occasionally, and my car has a hesitation when cold. Thanks

 

DTC16 is loss of low res pulse from the Opti. This is a "stored" code, because if DTC16 is "active" the PCM shuts down the fuel system. It is not unusual to see this as a stored code.... could just be an occaisional startup glitch in the Opti, or could be a sign the Opti is going to fail soon. You could check the wiring harness connector to make sure there is no sign of corrosion.

DTC42 is "IC circuit grounded". This can be a continuity or component problem anywhere in the ignition circuit, starting with the "fire" signal from the PCM (white wire to Ignition control module), problem with IC module, the feed from the IC module to the coil, or shorts anythwere in the wiring systems for these components. There is an "analysis" tree in the GM manual that walks you through the steps required to identify the problem.

DTC44 is lean reading on driver's side O2 sensor. Could be:
-faulty sensor
-sensor wire contacting manifold
-MAF sensor miscalibrated
-bad sensor ground
-low fuel pressure
-fuel contamination
-exhaust leaks before the O2 sensor
-misfires.
-large vacuum leak
You really need a complete scan data log to read the long term fuel corrections... that will tell you when the problem is most pronounced, and whether it is just a "driver's side" problem, or whether it is just as bad on the passenger side, but not quite enough to set DTC 64

There is no DTC52 as far as I am aware. They used it on the earler models for "CALPAC error". The current PCM's use DTC51 for EEPROM programming error.

What year is your car? (Always a good idea to include this info in a "signature", since the answers can depend on the year of the car). For example, maybe the 93's still use DTC52 because they do have a plug-in chip??????