My GST has been having issues for awhile now. It starts everytime, but 3/4 the time it only runs on two cylinders. Some times it starts right up, but eventually goes back to two cylinders. I have narrowed it down to three things, Powertrain Control Module, Crankshaft position sensor, or the Camshaft position sensor. If anyone knows how to troubleshoot any of these things your help would be greatly appreciated. Thank you for your time.

try checking the ECU first. smell it for burnt electronics. if that doesnt work check your plugs and plug wires. do a compression test to check for a blown headgasket.


You didn't mention what you have tried yet so I'm just trying to toss out the free things before you try replacing sensors.

any mods? did you get your diagnoses from engine codes (CEL's) or just what you were thinking could be the problem?

I had this problem. I was firing on cylinders 1 and 4 (coil #1). So i switched the coils. I still fired on cylinders 1 and 4 except this was coil (#2) and coil (#1) did not fire at all.

If you have this prob, the source is the power transistor. it is located right under the fuel rail and above the intake mani.

i apologize for not putting what i have already tried. I started off with new plugs. When that didn't work I checked for spark in the coil. I was getting spark from #1 and #4 only. I replaced the coil pack that was not working. She worked for about an hour. Did another spark test, #2 and #1 were getting spark but not #1 or #4. I replaced that coil pack, still nothing. Replaced all the plug wires to no prevail. I will check the ECU. Thank you all for your input.

I will post a pic when possible of the module that i had to replace, but look into the ignition power transistor

Thanks a lot man. That would be very helpful.