New and I need some help with SES codes.

**mczerwonka** · 01-27-2007, 09:39 PM

I have had this car for about 6 months and just recently it has this problem. The car will run relatively well in closed loop, but as soon as it switches to open loop the fun begins. The car will surge, misfire, and sometimes stall and the tach will occasionally bounce erratically. If it stalls I have to wait until it cools down again to even get it started, and in some cases if I baby it I can make it home. The odd thing is that it doesn't happen every time, but it will happen most of the time. The times it doesn't stall I just have to keep it below 2500 rpms and limp home. Instead of blowing $ at a mechanic I figured I would pull the DTC codes and ask for help. I used Data Master EE, because it was free (for at least the first 20 runs) and this is what I got. 13 (Bank 1 (left) Heated Oxygen Sensor (HO2S) Circuit (open circuit)) , 16 (Distributor ignition system (low resolution pulse) , 41 Ignition Control (IC) circuit (open circuit), 63 Bank 2 (right) Heated Oxygen Sensor (HO2S) Circuit (open circuit). I know that DTC 16 is possibly the opti spark, and the opti was replaced not but 3K miles ago (1 year ago), and I have no idea what 41 is, but I am thinking opti-spark as well. Now forgive me for my ignorance but could all my problems be with my PCM or would there be more error codes? They only reason I ask is that when I play back the file, the moment the system goes into open loop all the DTC's just pop up.

I am not saying that the car was running perfect in closed loop, but it was running much better. Another question I have is about 13 & 63. In looking at the recorded play back file the O2 mV was ranging from 100-900 in closed loop. As soon as it went to open loop the O2 mV for the Left will stay at 448 -450 mV and the Right will jump from 457 -475 mV.
I am lost cause the O2 mV readings seemed fine before the system went into open loop.

Any help with these codes would be greatly appreciated. Thanks in advance for your help.

1994 Firebird, 383,6spd,LT4 heads, 58mm t/b, Hooker long tube headers, 3" straight exhaust, Vortech t-trim supercharger

**Wheeler99WS6** · 01-28-2007, 03:58 AM

wow...I thought all 4th gens started in open loop then switched to closed loop, your is the opposite. I bet that sux as in gas mileage. I dont know anything about opti-spark stuff, but I would try changing my 02 sensors if I was you and see if it helps.

**Sarge** · 01-28-2007, 04:33 AM

I went through this same thing so many times trouble shooting these LT's. And almost without exception it has been the ECM. I would do two things here and neither are expensive nor a PITA to do. And you shared the tach was boucing ( big give away for a erratic/bad ECM)
1. I'd replace the Oxygen sensors. They are cheap at NAPA/AutoZone etc. Around $50 bucks.

2. Change out the ECM. Cheap at NAPA or AutoZone....around $120 bucks. You can get them reflashed cheap.
Often I found with a bad ECM you can tap on them and all of a sudden your car runs great....try it...
Opti is another story but I just do not sense an Opti problem here....

**Steve Crowe** · 01-28-2007, 07:46 AM

Step back and look at what the codes are telling you. You've got two O2 sensor open circuit codes, what's the chance of both going bad at the same time? About -0-.

You've probably got a problem in the wiring harness or one of the large connectors that goes to the PCM. And yes, it is possible the PCM is at fault, probably $50 for one froma reputable salvage yard.