Hello all, I am new to the site. I just bought my second VETTE. It is a 1994 black on black 6 spd. I couldn't get rid of my older one. It is a 1984 auto, so i gave it to my wife for a play toy.

All of a sudden the car started running rough and was bucking.

My question is. Is this car a OBDII or OBDI? I know that in 94 and 95 GM started introducing the OBDII in the VETTES. It has a OBDII conector. Over the weekend I had my SYS light blinking And i scanned it and it came up with two codes 160 and 161. Which is the rear O2 sensor. None of the part stores has a listing for that on my car. So i went home a jacked it up, found the sensor and realized that the white wire that is clipped to the body of the sensor had come off, so i cleaned the rust off of it and used a little hose clamp to put it back on. It seems to have worked. It didn't seem to be running as rough and i drove it for about a half hour and the light hasn't come back on yet.

 

For most intents and purposes it is OBD1.

What did you use to scan it with? There are no OBD1 codes for the rear O2. I wasn't aware you could get to the OBD2 codes with a normal scanner. If you don't know if it's OBD1 or OBD2 how did you scan it and how did you know what the code meant?

The rear O2 sensor will not set the sys light on these cars, and the rear O2 also has absolutely nothing to do with running rough, so all of this is very strange...

 

I scanned it with a Actron CP9145 scanner with the OBDII connector. The code that came up were 160 and 161. Code 160 is O2 sensor ckt no activity ( bank 2 sensor 2 ) Code 161 is O2 sensor heated circuit malfunction ( bank 2 sensor 2 ). I have a article somewhere that says that GM started puttimg OBDII in the Corvettes in 1994 and 1995.

 

What's the part number on the label on your PCM?

I'm wondering if you have a 96-97 PCM.

Again, regardless of PCM/OBD/anything else, rear O2s have nothing whatsoever to do with how the engine runs. And, as your car came from the factory, rear O2s will not set the SYS light.

 

I will take a look at it when i get home tonight. All i know is that when i hooked the white wire back up with a hose clamp the car started running better and the SYS light hasn't come back on yet.

 

The rear O2 WILL set an OBD2 code on a 94 or 95.

Codes P0158 (book 2 page 6E3-A-194), P0160 (book 2 page 6E3-A-196), P0161 (book 2 page 6E3-A-198), and P1158 (book 2 page 6E3-A-222) are all OBD2 codes and all are related to the O2 sensor, bank 2 sensor 2.

That is all in the 1994 GM service manual (and the pages are listed for each DTC listed ubove). The rear O2 isnt the cause of the SYS light though and the rear O2 is only to evaluate the efficency of the cat-converter on the right bank.

Use the paper clip method to get the DTC from Module 1 which will tell you why the SYS indication flashed.

 

I haven't tried to use a paper clip yet. I thought the scanner would tell me everything. What i don't understand is after i hooked up the broken wire on the rear o2 and cleared the codes the SYS light hasn' come back on again. Before i fixed the wire i would clear the codes the take the car out for a drive and within a couple of mins the SYS light would start flasging again.

One more thing i have noticed is that the climate control buttons are starting to act up. Sometimes i have to sit there and keep pushing them all to get it to come on. Any ideas??

I just bought the car about a month ago so i haven't had a chance to get a manual on it yet. The ones you uy at the parts store are junk.

The car only has 43000 miles on it and it has never seen rain. I was hoping to get longer than a month out of it before i started having problems.

Thanks for all the help.

 

Here is the paper clip method of code retrieval:

On a 94/95 you can check the codes with a paper clip as follows:

You short pin "12" to pin "4" and turn the ignition switch to "On" without starting the engine.

The speedometer will display any codes using the same protocol as the 1990-1993 model but there are some changes in the designation for the modules plus additional modules are added:

Module "1" is still the CCM module.

Module "4" is now called the PCM module (Powertrain Control Module) because automatic transmission computer control was added to Engine Control Module in 1994.

Module 7 (on the 1996 model only) is the RTD module. (This is the Real Time Dampening module which replaced the Selective Ride Control module in 1996).

Module 9 is the ABS/ASR module number from 1994 through 1996.
Finally, Module "A", the DERM (Dynamic Energy Control Module --- (the air bag control module) will be requested to show any codes.

Just like the 1990-1993 display, you read the codes on the speedometer (big) and read the module number on the trip odometer (small).

A series of dashed lines for instance “ - - -“ indicates no more stored codes for that module.

A code showing as “C12” for the CCM module (module #1) means no codes are stored. So C12 is a good thing to see.

Again, you can cause the codes to repeat by turning the ignition off for five seconds and then back on.

Turn the ignition off and remove the short to restore normal operation.

To clear the codes,

1. With ignition "off" ground terminal #12 of the DLC (use bent paper clip to connect pin 4 to pin 12)

2. Turn ignition "on".

3. Press trip/odo button on the DIC until 1.7 appears in the trip
monitor area of the instrument cluster.

4. Press eng/met button on the DIC & hold until "---" appears in the
speedometer area of the cluster, this will clear CCM DTC'S.


To clear PCM/ECM codes do the following:


1. Press the trip reset button on the DIC until the desired system is displayed. In this case it will be 4.0.

2. Press trip/odo button on the DIC until the desired diagnostic mode(4.7) is displayed on the trip monitor area of the cluster.

3. Press & hold the eng/met button on the DIC until "---" is
displayed in the speedometer area of the cluster, this will clear PCM codes.


To clear ABS/ASR codes do the following:

Same as above but you’re looking for “9.7” on the trip odo

And here are the codes

1994-1995: Diagnostic Trouble Codes
DTC #11: Malfunction Indicator Lamp Circuit.
DTC #13: Bank #1 Heated Oxygen Sensor #1 Circuit:
DTC #14: Engine Coolant Temperature Sensor Circuit Voltage Low.
DTC #15: Engine Coolant Temperature Sensor Circuit Voltage High.
DTC #16: Distributor Ignition System Low Pulse.
DTC #18: Injector Circuit.
DTC #21: Throttle Position Sensor Circuit Voltage High.
DTC #22: Throttle Position Sensor Circuit Voltage Low.
DTC #23: Intake Temperature Sensor Circuit Voltage High.
DTC #24: Vehicle Speed Sensor Circuit.
DTC #25: Intake Air Temperature Sensor Circuit Voltage Low.
DTC #26: Evaporative Emission Canister Purge Solenoid Valve Circuit.
DTC #27: EGR Vacuum Control Signal Solenoid Valve Circuit.
DTC #28: Transmission Range Pressure Switch Assembly Fault.
DTC #29: Secondary Air Injection Pump Circuit.
DTC #32: Exhaust Gas Recalculation.
DTC #33: Manifold Absolute Pressure Sensor Circuit High.
DTC #34: Manifold Absolute Pressure Sensor Circuit Low.
DTC #36: Distributor Ignition System High Pulse.
DTC #37: Brake Switch Stuck On.
DTC #38: Brake Switch Stuck Off.
DTC #41: Ignition Control Circuit Open.
DTC #42: Ignition Control Circuit Shorted.
DTC #43: Knock Sensor Circuit.
DTC #44: Bank 1 LF Heated Oxygen Sensor #1 Circuit Lean.
DTC #45: Bank 1 LF Heated Oxygen Sensor #1 Circuit Rich.
DTC #47: Knock Sensor Circuit Or Module Missing.
DTC #48: Mass Air Flow Sensor Circuit.
DTC #50: System Voltage Low.
DTC #51: EPROM Programming Error.
DTC #52: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #53: System Voltage Low.
DTC #55: Fuel Lean Monitor.
DTC #58: Transmission Fluid Temperature Sensor Circuit Low.
DTC #59: Transmission Fluid Temperature Sensor Circuit High.
DTC #62: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #63: Bank 2 RF Heated Oxygen Sensor #1 Circuit Open.
DTC #64: Bank 2 RF Heated Oxygen Sensor #1 Circuit Lean.
DTC #65: Bank 2 RF Heated Oxygen Sensor #1 Circuit Rich.
DTC #66: A/C Refrigerant Pressure Sensor Circuit Open.
DTC #67: A/C Pressure Sensor Circuit Sensor or A/C Clutch.
DTC #68: A/C Relay Circuit.
DTC #69: A /C Clutch Circuit.
DTC #70: A/C Clutch Relay Driver Circuit.
DTC #72: Vehicle Speed Sensor Loss.
DTC #73: Pressure Control Solenoid Circuit Current Error.
DTC #74: Traction Control System Circuit Low.
DTC #75: Transmission System Voltage Low
DTC #77: Primary Cooling Fan Relay Control Circuit.
DTC #78: Secondary Cooling Fan Relay Control Circuit.
DTC #79: Transmission Fluid Overtemp.
DTC #80: Transmission Component Slipping.
DTC #81: Transmission 2-3 Shift Solenoid Circuit.
DTC #82: Transmission 1-2 Shift Solenoid Circuit.
DTC #83: Torque Converter Solenoid Voltage High.
DTC #84: 3-2 Control Solenoid Circuit.(Auto Only).
DTC #84: 2nd And 3rd Gear Blockout Relay Control Circuit.
DTC #85: Transmission TCC Stock On.
DTC #90: Transmission TCC Solenoid Circuit.
DTC #91: One To Four Upshift Lamp(Manual Only).
DTC #97: VSS Output Circuit.
DTC #98: Tachometer Output Signal Voltage Wrong.

The codes listed there are only for module 4, when you find out what code is in module 1, post it up and ill tell you what it is.

Here is a pic of the 16 pin connector under the dash, pins 4 and 12 are what youre after:

 

Thank you all for all the help. I'm not going to get a chance to look at the car until this afternoon so i'll post what i find out tomorrow.

Are you telling me that the scanner i just bought wont work for my car? It's the Actron 9145.

I also forgot to mention that i took the car out last night and it is realy runing like crap. It is bucking and has a bad miss at idle, even worse with the air on.

 

No mate, the scanner is fine, it should work with the car if it pulled out those codes. Ive never used one of those particular scanners so i just dont know how to get to the CCM codes with it. The onboard system can display these on the digital instrument cluster for you though with a paper clip joining pins 4 and 12.

Let us know what you get out of there mate

 

I will post what i come up with. I am confused as to why did the SYS light not come back on after i fixed the white wire on the rear O2 sensor. Especially since i am hearing that the rear O2 will not trip the SYS light.

 

It wont, and it also wont set the Service Engine Soon light either.

SYS flashing on the instrument cluster means you have a DTC stored in the CCM, which is module 1.

 

Did anyone say otherwise?

 

Common problem. Can usually be fixed by cleaning the switch contacts. If you search in tech/performance there should be some threads on the subject.


Did you check the PCM P/N?

 

Ok, here is what i found by blinking the codes.

Module 1 ( H13 )

Module 4 ( --- )

Module 9 ( H72 )

Module A ( --- )

Thank you guys again for all your help.

Shawn

 

Section 8D in book 1 of the GM service manual will have the CCM Diagnostic info for ya.

H infront of the DTC means History. DTC 13 in module 1 is Driver information switches circuit: Open or shorted to battery voltage.

DTC 13 Will Set When: CCM senses a voltage aproximately equal to the 5 volt reference at the DIC switch detection imput for longer than 3 seconds. Book 1, pages 8D-20 and 8D-21 in the GM service manual will have the info for that.

Module 9 is for ABS/ASR DTCs. DTC 72 is a serial data line malfunction. Book 1, page 5E2-114 in the GM service manual will find you that one.

Did i say anyone did? I dont believe so....
What for??? If it was a 96 PCM it would be setting a heap of DTCs it has nothing for. And the Service Engine Soon light will come on for the 2nd O2 sensor on the right bank for a 96.

 

Thanks alot. As i said, i haven't had a chance to get a manual for it yet, but i will.

So it seems that there are no codes to help me out with why it is running like crap? It is sputtering at idle and bucking on acceleration. Originally i thought i got bad gas so i put some dry gas in itand i drove it last Sunday for 130 miles to try to get the gas out of it. ( i guess sometimes it's not too good to get great gas milage on the highway!!! LOL ).

Is it possible that the opti is going??? A buddy of mine has a 1994 Z28 that we had to put two optis in it before he finally said the hell with it and put a DelTech in.

Any more info would be greatly appreciated.

Thanks, Shawn

 

If a Delteq system fixed it there was nothing wrong with the optispark. Cap and rotor maybe, ICM possibly, coil, leads, any of that, but NOT the optispark. The optispark still needs to function for the Delteq setup to know what plug to fire and when.

If youre getting better mileage and its running poor, start by checking fuel pressures, and then be sure all injectors are getting a signal to fire, as well as ohm test each injector coil to make sure they are all ok. If they all test good cold as well as hot, consider having them ultra-sonically cleaned.

Plug in that scanner of yours and look for the long term BLM data that will indicate what the primary O2s are telling the ECM, if 1 or both the primary O2s are saying its rich and its actually lean, 1 or both of them may be on the way out.

Check the lead from the coil to the distributor, they have a bad habbit of wearing out against the back of the water pump and arcing. Check all the leads and the plugs (including the gap) and make sure that you have good strong spark at all 8. If you dont, it may not burn all the fuel, which will result in the O2s seeing abit of unburnt fuel and telling the ECM its a bit rich, it will take abit of fuel out to lean it up, the missfiring cylinder/s may or may not continue to release unburned fuel and the engine will run like ****.

Be sure to investigate everything thoroughly before replacing what could be a perfectly good part, cause replacing good parts leaves you back at square 1

 

It's not that i'm getting better malage, I was just saying that because it took me a while to burn the fuel out of the car because of the awesome milage they get.

I have the O2 readings

O2 left ( mv ) fluxuating between 40 to 850 while running
O2 right ( mv ) SAME

I put new plugs in it. I used NGK V- power Gapped at .050. The old ones looked fine. Is there a different one i should have used??
Thanks, Shawn

 

You can use what ever is the right length, and that gap is fine. I use NGK TR-55 IX (or something like that).

Seems like those O2s are working as they should (which doesnt mean they are accurate), so proceed with the other checks there and see what you come up with.

Check to make sure its not getting fresh air sucked in anywhere or the EGR valve is opening when it should be shut.

CO test the coolant as well, and if you get a bad reading from that, step up to a compresion test, and a leak down test.

You never know, lots of things could cause it, so you want to check the health of all of it.