1994 Corvette Diagnostic testing

[Edward V.]

The 1994 Corvette has a 16 pin ALDL connector similar to the 16 pin OBD2 connector on 96 Corvette and later. Can a CanOBD2 Scanner be used on the 94 Corvette connector to scan and reset trouble codes? Is there a potential for circuit damage using a CanOBD2 Scanner?

Ed

[David T.]

Re: 1994 Corvette Diagnostic testing

I don't think an OBD-2 Scanner would hurt your circuit, but I don't think it will work correctly on the 94-95 Vettes. They are still basically OBD-1 even though they have the newer OBD-2 connector under the dash. OBD-2 was not fully implemented until the 1996 model year. Here's a link that will show you how to interrogate your system by jumping 2 pins with a paperclip. It will display any stored codes, but will not let you erase them.

http://tech.corvettecentral.com/2011/01/c4-diagnostic-trouble-codes/

Good Luck,

Dave T.

[Mel H.]

Re: 1994 Corvette Diagnostic testing

FWIW.. Had same issue with my 94. Tried OBD2 but repeatedly showed 'error' and would not read the codes. Eventually just tried the paperclip trick.. surprisingly easy and worked well.

Mel

[Joe L.]

Re: 1994 Corvette Diagnostic testing

The 1994 Corvette has a 16 pin ALDL connector similar to the 16 pin OBD2 connector on 96 Corvette and later. Can a CanOBD2 Scanner be used on the 94 Corvette connector to scan and reset trouble codes? Is there a potential for circuit damage using a CanOBD2 Scanner?

Ed

Ed------


There are scanners available that will work with both OBD I and OBD II systems. The Inova 3140 is one of them. Of course, when scanning an OBD I system it won't provide as much information as when scanning an OBD II. However, the Inova 3140 uses different cables for OBD I and OBD II systems. I just don't know how it would work for those few model years that use an OBD II connector with an OBD I system.

[Terry M.]

Re: 1994 Corvette Diagnostic testing

I don't know how that scanner (Inova 3140) works with the OBD II connector, but my Caprices both have OBDI with the OBDII connector and the cable that came with my OBDI scanner plugs right in. I can't recall the brand at the moment, but I can look tonight. I had to upgrade for the OBDII in the Camaro and the daughters Malibu, and will have to do the upgrade again for the CAN system in the 2008 Corvette one of these days. Upgrading test equipment is a continual burden.

I used to see inexpensive (<$100) OBDI scanners all the time in the Sunday sales papers, but not so much any more. OBDI is about to go the way of the Dodo bird. If you can find a scanner that is backwards compatible at a reasonable cost (whatever that is for your pocketbook) you had better jump on it while you can.

[Bill H.]

Re: 1994 Corvette Diagnostic testing

I saw one guy trying to use a OBD I scanner with the I to II cable on his 94. The codes came up wrong. I think it was an Actron scanner (we were at the race track and didn't have much time). I sent him the dash procedure and that worked fine.

You can clear codes on a 94-95 using the dash.
This is the procedure I use:
On a 94-96 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


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.

Here are the codes for the keyless entry.

And the PKE diagnostic system works as follows:

With pins 4 and 8 connected, the PKE light in the Driver Info Centre will flash the codes.

Here is the list of DTCs and what they mean:

DTC #12: Receiver Memory Bad
DTC #13: Transmitter Not in Range
DTC #14: Non-Valid Transmitter Received
DTC #15: Valid Transmitter Received
DTC #16: Passenger Door Button Depressed
DTC #17: Hatch Button Depressed

[David H.]

Re: 1994 Corvette Diagnostic testing

CLEAR DTCs: An OBD I scanner should clear DTCs. However, I believe that if you disconnect power feed to the ECM PCM VCM for 30 seconds it will clear DTCs. Disconnecting the negative battery cable will also clear DTCs, but will also clear memory data like radio presets as well. (Be sure ignition key is OFF when disconnecting/reconnecting power feed.)

Disconnecting the battery also puts the system into "learning". Vehicle performance may be changed as the learning process resets (begins again). "Teach" happens with the engine at operating temperature and the car driven at part throttle, moderate acceleration, and idle.

[Edward V.]

Re: 1994 Corvette Diagnostic testing

Joe,

I have an Innova 3100, however it has only a OBD2 cable and I don't believe it is OBD!1capable.

Thanks, Ed

[Edward V.]

Re: 1994 Corvette Diagnostic testing

Bill,

Thanks for all the information on the codes and their meanings. I believe from the discussions so far that I will use the paper clip method.

Ed

[Edward V.]

Re: 1994 Corvette Diagnostic testing

David,

Good info.

Thanks, Ed

[Bill H.]

Re: 1994 Corvette Diagnostic testing

Bill,

Thanks for all the information on the codes and their meanings. I believe from the discussions so far that I will use the paper clip method.

Ed

I couldn't get the picture of the ADL connector to post but the hole locations to jump ara shown in the kink David posted, post #2.

[Edward V.]

Re: 1994 Corvette Diagnostic testing

Bill,

I got it pins 4 & 12. I tried it earlier today and it worked fine. No trouble codes.

Ed