C4 Gurus, please help!
Thread Starter
Cruising
Joined: Mar 2006
Posts: 12
Likes: 0
From: Los Angeles CA
C4 Gurus, please help!
I have a 1994 C4 automatic coupe with 88,000 miles. the car was good until today. It started to buck and missfire pretty badly, so I pulled into my driveway and shut it down. A couple minutes later I tried to start it and absolutely nothing happens. No starter cranking, nothing. Yes, the battery is fine, I have full bright headlights and the instruments come alive and light up. When I turn the key to the "on" position, the "security" light on the lower left instrument cluster blinks a few times, and stays lit, but the car won't start.
Any ideas what this might be? Can I pull codes from the computer to help diagnose this? If so, how do I do that?
The car has never done this before, and it was only drive about 5-10 minutes when this occurred, so it wasn't fully warmed up yet, if that makes any difference.
thanks for any help.
Any ideas what this might be? Can I pull codes from the computer to help diagnose this? If so, how do I do that?
The car has never done this before, and it was only drive about 5-10 minutes when this occurred, so it wasn't fully warmed up yet, if that makes any difference.
thanks for any help.
Team Owner
Joined: May 2006
Posts: 21,473
Likes: 356
From: Palmdale, Ca----- 2009 Cyber Gray 4LT A6 F55 452 RWHP 422 RWTQ- RIP 1998 C5 734 RWHP & 585 RWTQ-----
Try to pull codes on the computer to see if there is any. I know you said you don't know BUT go to this Forum and at the Top you will see a "SEARCH" mouse on the arrow drop the box down and type in "How to get codes from 1994 Vette" or whatever might work it will pull up a lot of older threads that might be helpful. I hope this helps.
ONE SUGGESTION-You might want to fill out your personal profile if you do more might be willing to help.
Thanks, Matt
ONE SUGGESTION-You might want to fill out your personal profile if you do more might be willing to help.
Thanks, Matt
Thread Starter
Cruising
Joined: Mar 2006
Posts: 12
Likes: 0
From: Los Angeles CA
more info
OK, some more info:
Yesterday when the car wouldn't start, the security light came on as usual when the door was open, but it didn't go out when the key was turned on. The car wouldn't start, the starter wasn't even engaging.
this morning the car started up normally and ran great. The security light behaved as follows:
When the door was open, the light blinked, as soon as I turned the key on, the light went out and the engine started.
So maybe I have an intermittent issue with the security system?
any way to check this out?
thanks
Yesterday when the car wouldn't start, the security light came on as usual when the door was open, but it didn't go out when the key was turned on. The car wouldn't start, the starter wasn't even engaging.
this morning the car started up normally and ran great. The security light behaved as follows:
When the door was open, the light blinked, as soon as I turned the key on, the light went out and the engine started.
So maybe I have an intermittent issue with the security system?
any way to check this out?
thanks
Racer
Joined: Apr 2005
Posts: 408
Likes: 0
Your key has a metallic pellet built into it. It gives a resistance specific to the car to the security system. If this is dirty, or the contacts in the ignition itself are dirty, then the resistance value will be off, and the car will not start for a certain number of minutes before you can try it again.
This does not explain the bucking and misfiring however. Once the car is started, it no longer looks for the resistance value on the key.
This does not explain the bucking and misfiring however. Once the car is started, it no longer looks for the resistance value on the key.
Thread Starter
Cruising
Joined: Mar 2006
Posts: 12
Likes: 0
From: Los Angeles CA
OK, that is a very good possibility. Any idea how long the duration is before you can attempt a re-start?
As far as the bucking/stalling, I put gas into the tank (it had probably a gallon or so left at the time) and it runs great now. Is there a "fuel accumulator" on this FI system? If so, it may be defective.
thanks so far for the assistance.
BTW, I updated my profile. :-)
As far as the bucking/stalling, I put gas into the tank (it had probably a gallon or so left at the time) and it runs great now. Is there a "fuel accumulator" on this FI system? If so, it may be defective.
thanks so far for the assistance.
BTW, I updated my profile. :-)
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by lt4red
Your key has a metallic pellet built into it. It gives a resistance specific to the car to the security system. If this is dirty, or the contacts in the ignition itself are dirty, then the resistance value will be off, and the car will not start for a certain number of minutes before you can try it again.
This does not explain the bucking and misfiring however. Once the car is started, it no longer looks for the resistance value on the key.
This does not explain the bucking and misfiring however. Once the car is started, it no longer looks for the resistance value on the key.
This sounds like you VATS. More than likely lt4red is right. If they key or ingition is worn there will be a miscontact and the starter will not engage. If you have a backup key try that. The resistance on the key can be ohmed and the key numbers will be between 1-15. You can use an ohm meter and use on each side of pellet and give the ohm numbers back here and we can tell you what number it is. Or you can take the key to Radio Shack or GM and they can read it for free and a spare key can be had from anywhere between $5-25 depending on where you get it. The time on restart is about 10 min.
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
Originally Posted by lt4red
This does not explain the bucking and misfiring however. Once the car is started, it no longer looks for the resistance value on the key.
-- Joe
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
If your gas gage is really off that far you might want to check out this post to get your fuel gauge more accurate. It may also save your fuel pump from overheating with insufficient fuel in tank.
http://forums.corvetteforum.com/show....php?t=1373669
http://forums.corvetteforum.com/show....php?t=1373669
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Racer
Joined: Apr 2005
Posts: 408
Likes: 0
Originally Posted by anesthes
This is true for LT1/LT4 PCM behavior? I know in $32 for sure it checks vat s constantly in the main loop. $8D looks like it only checks it once initially, but I think it calls the routine again during diagnostics. $6E I dont have a hack for to verify, and I havn't even looked at the LT1 stuff. (though with the cyl trim and all that it looks like a great ECM!)
-- Joe
-- Joe
However, the ccm also sends a signal over the serial data lines to the ecm to allow fuel injector pulses to begin. Once this happens the ecm sends a message back to the ccm that feds, or fuel enable data stream, has been succesfully completed. The manual doesn't say anything about a continuous monitoring.
Also the system disable is for 3 minutes. It will do nothing for that amount of time even if the correct resistance value is received from the key.
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
This doesnt sound like VATS to me, VATS wont cause a misfire..... Here is the code retrieval procedure.....
On a 94 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
1994-1996: 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.
Check and see what you have there, code C12 is fine, and you should get this code. 'H' infront of a number means 'history' or past issue which is not recently present, 'C' means 'Curent' or still an ECM known present issue.
On a 94 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
1994-1996: 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.
Check and see what you have there, code C12 is fine, and you should get this code. 'H' infront of a number means 'history' or past issue which is not recently present, 'C' means 'Curent' or still an ECM known present issue.
Last edited by Casethecorvetteman; Jun 1, 2006 at 12:59 PM.
Heel & Toe
Joined: Sep 2005
Posts: 16
Likes: 1
BCM going bad?
LA Cruiser -- just FYI ..... son has a 96 CE LT-1 automatic. Several times in 2 months, car wouldn't crank after normal stop. Would crank and start after sitting several hours...... but 3d time wouldn't do squat. Towed to shop, it scanned (not with a code reader, rather, a much more expensive shop-only type) as bad key, replaced key and ignition switch, etc. Looooong story short, had to replace the BCM (body control module). $1600 total (OUCH!) about half of that was for the BCM (new.) got car back showing 0 miles, now trying to get car re-flased to show actual mileage. (Anyone know how?) Can find used BCM's on web for about $100 or a bit more. May show wrong mileage, though.
covetteman.... cool post re pulling OBD codes.... had always read they couldn't be pulled without a scanner!! (and yes i did spend $400 for a good scanner!) oh, well.
covetteman.... cool post re pulling OBD codes.... had always read they couldn't be pulled without a scanner!! (and yes i did spend $400 for a good scanner!) oh, well.
Racer
Joined: Apr 2005
Posts: 408
Likes: 0
Originally Posted by docimastic
LA Cruiser -- just FYI ..... son has a 96 CE LT-1 automatic. Several times in 2 months, car wouldn't crank after normal stop. Would crank and start after sitting several hours...... but 3d time wouldn't do squat. Towed to shop, it scanned (not with a code reader, rather, a much more expensive shop-only type) as bad key, replaced key and ignition switch, etc. Looooong story short, had to replace the BCM (body control module). $1600 total (OUCH!) about half of that was for the BCM (new.) got car back showing 0 miles, now trying to get car re-flased to show actual mileage. (Anyone know how?) Can find used BCM's on web for about $100 or a bit more. May show wrong mileage, though.
covetteman.... cool post re pulling OBD codes.... had always read they couldn't be pulled without a scanner!! (and yes i did spend $400 for a good scanner!) oh, well.
covetteman.... cool post re pulling OBD codes.... had always read they couldn't be pulled without a scanner!! (and yes i did spend $400 for a good scanner!) oh, well.
Also your sons 96, is OBDII and the codes for the engine control module do need a scanner to be pulled. Codes for other systems can be accessed, but not the engine/emissions.
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
Originally Posted by docimastic
...... (Anyone know how?) Can find used BCM's on web for about $100 or a bit more. May show wrong mileage, though.
covetteman.... cool post re pulling OBD codes.... had always read they couldn't be pulled without a scanner!! (and yes i did spend $400 for a good scanner!) oh, well.
covetteman.... cool post re pulling OBD codes.... had always read they couldn't be pulled without a scanner!! (and yes i did spend $400 for a good scanner!) oh, well.
