A friend of mine bought a 1985 Camaro with a LT1 in it a few months back. The motor came out of a 1995 Camaro. It has a Delphi Automotive OBDI computer #16159278 which I think is for a 1993 application.

The car ran fine for 2 months, then it started to just die. Sometimes when it was at operating temps, sometimes when it was warming up, and sometimes it would not start when it was stone cold. Very intermittent. Tried a new coil. No change.

I held off on trying to pull the codes because I had no idea what type computer it had in it yet. The first time I pulled the codes I was checking them against the wrong table, the one for an ’85. The TPS seemed to be the culprit so I went that route. While looking at the TPS I noticed the TB was nasty dirty. I had a clean one with known good components on it so I installed it. The car ran a little better but would still die.

I hooked a fuel pressure gauge to it. Fuel pressure stayed rock steady when it would die, so I ruled that out.

I tried to hook up a laptop to do some data logging. I couldn’t establish communication with the computer. Tried 3 laptops, 2 cables, and several data logging problems. No joy. All of them would work on my ’91 Firebird though. This sux.

Continuing with the troubleshooting, I found the wires going to the TPS has some electrical tape on them. Wires were nicked. I cut them, soldered them and covered with heat shrink sleeves. Still had same problem.

I finally dug out the computer to see what kind it was. Now the codes started making sense.

22 – TPS
26 – Evap purge control solenoid
36 – DIS
44 – LEAN EXHAUST
64 – Rt bank O2 sensor

So now I’ll start troubleshooting the ignition system. Wish I could get a data logger to work. An opti is a lot harder to swap out than a coil. LOL

Anybody have any suggestions? I really need to get this car running and out of my driveway. Thanks.

 

If you have a 93 ECM, you have to use the 93 code list. Were you able to flash the codes on the SES light by shorting the ALDL pins? That would confirm its a 93 ECM, and not the later 94 PCM. And... do you have an MAF sensor, or not? 93 is speed-density, no MAF sensor.

93 Codes:

DTC 22 = Throttle Position (TP) sensor circuit (signal voltage low).

This means the TPS voltage was below 0.20V for 3 seconds. Hook up a volt meter across the gray reference voltage wire and the black ground. ECM should be providing 5V reference signal. Then measure the voltage across the blue signal wire and the black ground wire. At close throttle, the voltage must be in the range of 0.20-0.90V, with something in the range of 0.50-0.70V prefered. If its OK at closed throttle, slowly rotate the blades, and watch for the voltage to increase smoothly at WOT to about 4V higher than the closed throttle voltage. Look for dropouts in the signal as the blades rotate. While you are performing these tests, jiggle the harness wires to make sure you don't have a fault in the wires.

DTC 26 = Quad-Driver Module (QDM) #1 circuit
applies to:
- AIR pump relay circuit
- EGR solenoid
- EVAP solenoid

Do you have all these systems connected in the new application? Typically, its either a blown fuse for the AIR pump, or a wire or solenoid problem on the EVAP and EGR systems.

DTC 36 = Distributor ignition system (faulty high resolution pulse or extra low resolution pulse detected)

Check the two harness connectors for the Opti - the one on the side of the intake manifold and the one that plugs into the Opti. Look for bent pins or corrosion.

DTC 64 = Bank 2 (right) Oxygen Sensor (O2S) Circuit (lean exhaust indicated)

O2 sensor or wire fault, misfires on the right bank, faulty injector, exhaust leaks before the O2 sensors - would affect only one bank.

low fuel pressure, contaminated fuel, MAP sensor reading low - would affect both sides of the engine.

What diagnostic software are you trying to use? Diacom?

 

Thanks Fred. I did a harness shakedown. That's how I found the nicked wires a few inches up from the TPS sensor. I checked the Opti connectors and they looked good. I could not get the engine to react at all when I vigorously wiggled the opti harness.

I think I tried Winaldl, EFILive, Freescan, and Scantool. I really want to get a scanning program so I can see what exactly is crapping out. Any ideas on software that will work with this computer?

 

Can anyone suggest a logging program that will work with this setup?

 

I use TTS Datamaster
http://www.ttspowersystems.com/DataM...downloads.html
comes w/20 free sessions. This will pull the codes and tell you what they are.

Assume he has the ALDL installed correctly?

 

After I used the TTS program that was designed for the PCM in the car everything worked fine. I attached a link to a scan. The car ran for 2 minutes and 20 seconds before it abruptly shut down. RPM kicked up to 1100 for about 1/10 of a second right at shutdown. Don't know if that is normal or not. This is my first stab at reading a scan so I'll need some help.

The only anomaly I can see is between the left and right O2 crossover counts. Left was steady at 1, right was hanging over 200 until just over a second before shutdown.

Comparing the left and right O2 volts I can't make sense of the difference in the cross count. I'll be checking the right O2 sensor and wiring like Fred said to do when I get a chance.

Any other ideas? BTW, the car was cold when I did this run. Thanks.

http://www.mediafire.com/?sharekey=2...db6fb9a8902bda

 

You have logged it, did you change any of the sensors that the codes were for?
And did you make a list of the codes it was throwing as shown in the log file?

 

I haven't had a chance to throw ant sensors at it yet. Probably will Saturday. I'll have to check when I get home to see the 2 codes it threw.

Could the right O2 sensor doing what it shows in the log cause it to have an uncommanded shutdown like it did?

 

The trace shows temp was around 105*F (40.3) and the left and right O2 voltages are sitting at the .450MV range that says you are still in open loop. The right O2 is starting to switch (CCNT) but the left O2 is still cold. At record 736 the TPS voltage, IAC count, injector BPW, RPM, MAP, ign. voltage all look good & rock solid until 737 when RPM spikes +300 RPM. It looks like the PCM (IAC count) started to correct for the RPM spike in records 737-738 so it's seeing it also. Remember TTS only snapshots 8 times a second that's one every 13 revolutions at 800 RPM so a lot can happen between records. As Shon asked above, did you throw any codes ?? I would suspect to see high or low resolution failures from the OPTI . If the opti is putting out bad level or noisy signals to the PCM this can cause erroneous RPM readings and the PCM shuts down the engine.
My TTS version EE for the '94 has the DTC's displayed from a tab up top of the screen, is that missing from the '93 version ?.

 

Its on the '93 version but I don't remember right off hand what the two codes that it threw were. They were probably 34 and 64 though. I have them written down at the house.

 

It only threw one code - 36. I looked at the full run again and saw that the right O2 crossover count was constantly cycling from 5 to 250 every 4 1/2 seconds from the time I cranked it up till the time it shut down. It was about a second into that cycle when it shut down.

 

The Opti low res code (DTC 16) sets if the PCM loses the signal (no pulses) for 760 high res pulses. That's the one that shuts the fuel system down.

DTC 36 sets on the 93 if the PCM sees less than 60 high res pulses between each low res pulse. An erratic high res signal could cause your problems, although is shouldn't cause a complete shutdown.

At 141 seconds, you're still in open loop, so concerns about the O2 sensors being the cause would not seem valid.

800 rpm = 13.3 rev/sec. At a scan rate of 8/sec, that would be 1.67 rpm/scan.

 

is this right?
36 ignition system circuit error
http://www.extreme-check-engine-ligh...%20Decoder.htm

 

I guess its time to give the opti and associated wiring a closer look, eh?

 

Sort of, but its a generic description. Just use Shoebox's LT1 code list:

http://shbox.com/1/Dtcs.htm

DTC 36 = Distributor ignition system (faulty high resolution pulse or extra low resolution pulse detected)

The diagnostic evaluator is different between the OBD-I and OBD-II PCM's. OBD-I looks for at least 60 low res pulses between each high res pulse. OBD-II looks for 80 low res pulses occuring, without a pulse from the high res signal.

As noted in the GM manual for 92-93 Optis: