Optispark, Electrical, Fuel Pump, or Other Problem...Need Help!
Thread Starter
Advanced
Joined: Jul 2012
Posts: 70
Likes: 0
Optispark, Electrical, Fuel Pump, or Other Problem...Need Help!
Hello Everyone,
I'm currently having an issue with my Corvette(1994), I'll start off with the problem. Yesterday, I was heading to lunch around 12pm and 2 miles away my car died and I had to pull over to the side of the road. Luckily, there was a tow truck driver behind me that offered to take my car back to work. When the car got back to the work parking lot it started right up, so I thought maybe everything was ok. At 3:30 I went out and started my car back up, it idled great, but died 5 minute later. I wasn't going to chance driving it anywhere so I had it towed back home. After I got off work today I started' the car up and let it idle for 30 minutes and it DIDN'T die! I don't want to drive the car anywhere until I figure out the problem because rush hour traffic is horrible and I don't want to make it worse.
I've read a lot of forums and the consensus seems to be that it's probably the optispark, but I want a second opinion. I checked the codes in the computer and it was reporting back H16 and H72. So do you guys think it's the computer, optispark, fuel pump(I can here it prime when I turn the key), or something else??? Thanks for your responses in advance!
Optispark, Electrical, Fuel Pump, or Other Problem...Need Help!
I'm currently having an issue with my Corvette(1994), I'll start off with the problem. Yesterday, I was heading to lunch around 12pm and 2 miles away my car died and I had to pull over to the side of the road. Luckily, there was a tow truck driver behind me that offered to take my car back to work. When the car got back to the work parking lot it started right up, so I thought maybe everything was ok. At 3:30 I went out and started my car back up, it idled great, but died 5 minute later. I wasn't going to chance driving it anywhere so I had it towed back home. After I got off work today I started' the car up and let it idle for 30 minutes and it DIDN'T die! I don't want to drive the car anywhere until I figure out the problem because rush hour traffic is horrible and I don't want to make it worse.
I've read a lot of forums and the consensus seems to be that it's probably the optispark, but I want a second opinion. I checked the codes in the computer and it was reporting back H16 and H72. So do you guys think it's the computer, optispark, fuel pump(I can here it prime when I turn the key), or something else??? Thanks for your responses in advance!
Optispark, Electrical, Fuel Pump, or Other Problem...Need Help!
Le Mans Master
Joined: Dec 2006
Posts: 5,139
Likes: 482
From: H-Town Texas
http://www.gmtuners.com/OBD1_DTC.htm
H stands for history, as in not current.
16 is system voltage too low
72 is VSS signal circut error
My first suggestion is to check your ICM. It is located just above the coil. It is mounted to the heat sink that the coil is mounted to. It is held in place by two 7 mm bolts and is easily removed. Take it to an auto parts store and they can test it for you. If it tests bad, of course replace it. If it tests good, get some heat sink grease and apply a nice coat on the back and put it back on.
Then...using the spark tester you bought while you were at the parts store, when the car dies, check for spark from the coil.
If you have good spark, check for spark from the coil wire at the opti end.
If you have spark there, check for spark at the plugs.
I there is spark, your issue is fuel.
If there is no spark at the plugs but there is going to the opti, it's the opti.
If you have no spark from the coil, it's either the coil, the opti, or the ecm.
From there, check for voltage going to the coil.
If theres voltage, then it's the coil. If not, then check for voltage coming from the opti at the opti harness.
If there's no voltage, it's the opti, if there's voltage its the ecm.
Now, if the car just dies, as in no warning, no misfire, no otherwise bad behavior, it just quits, I'm going to bet on the icm. The heat sink wears over time, and when these overheat, they simply quit. A bad Fuel pump or regulator will act like it's out of gas and sputter then die. A bad opti could just quit, but typically will miss, backfire, then quit. But it really sounds like yours is heat related. Of course, I reserve my American Right to be wrong.
H stands for history, as in not current.
16 is system voltage too low
72 is VSS signal circut error
My first suggestion is to check your ICM. It is located just above the coil. It is mounted to the heat sink that the coil is mounted to. It is held in place by two 7 mm bolts and is easily removed. Take it to an auto parts store and they can test it for you. If it tests bad, of course replace it. If it tests good, get some heat sink grease and apply a nice coat on the back and put it back on.
Then...using the spark tester you bought while you were at the parts store, when the car dies, check for spark from the coil.
If you have good spark, check for spark from the coil wire at the opti end.
If you have spark there, check for spark at the plugs.
I there is spark, your issue is fuel.
If there is no spark at the plugs but there is going to the opti, it's the opti.
If you have no spark from the coil, it's either the coil, the opti, or the ecm.
From there, check for voltage going to the coil.
If theres voltage, then it's the coil. If not, then check for voltage coming from the opti at the opti harness.
If there's no voltage, it's the opti, if there's voltage its the ecm.
Now, if the car just dies, as in no warning, no misfire, no otherwise bad behavior, it just quits, I'm going to bet on the icm. The heat sink wears over time, and when these overheat, they simply quit. A bad Fuel pump or regulator will act like it's out of gas and sputter then die. A bad opti could just quit, but typically will miss, backfire, then quit. But it really sounds like yours is heat related. Of course, I reserve my American Right to be wrong.
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
http://www.gmtuners.com/OBD1_DTC.htm
H stands for history, as in not current.
16 is system voltage too low
72 is VSS signal circut error
My first suggestion is to check your ICM. It is located just above the coil. It is mounted to the heat sink that the coil is mounted to. It is held in place by two 7 mm bolts and is easily removed. Take it to an auto parts store and they can test it for you. If it tests bad, of course replace it. If it tests good, get some heat sink grease and apply a nice coat on the back and put it back on.
Then...using the spark tester you bought while you were at the parts store, when the car dies, check for spark from the coil.
If you have good spark, check for spark from the coil wire at the opti end.
If you have spark there, check for spark at the plugs.
I there is spark, your issue is fuel.
If there is no spark at the plugs but there is going to the opti, it's the opti.
If you have no spark from the coil, it's either the coil, the opti, or the ecm.
From there, check for voltage going to the coil.
If theres voltage, then it's the coil. If not, then check for voltage coming from the opti at the opti harness.
If there's no voltage, it's the opti, if there's voltage its the ecm.
Now, if the car just dies, as in no warning, no misfire, no otherwise bad behavior, it just quits, I'm going to bet on the icm. The heat sink wears over time, and when these overheat, they simply quit. A bad Fuel pump or regulator will act like it's out of gas and sputter then die. A bad opti could just quit, but typically will miss, backfire, then quit. But it really sounds like yours is heat related. Of course, I reserve my American Right to be wrong.
H stands for history, as in not current.
16 is system voltage too low
72 is VSS signal circut error
My first suggestion is to check your ICM. It is located just above the coil. It is mounted to the heat sink that the coil is mounted to. It is held in place by two 7 mm bolts and is easily removed. Take it to an auto parts store and they can test it for you. If it tests bad, of course replace it. If it tests good, get some heat sink grease and apply a nice coat on the back and put it back on.
Then...using the spark tester you bought while you were at the parts store, when the car dies, check for spark from the coil.
If you have good spark, check for spark from the coil wire at the opti end.
If you have spark there, check for spark at the plugs.
I there is spark, your issue is fuel.
If there is no spark at the plugs but there is going to the opti, it's the opti.
If you have no spark from the coil, it's either the coil, the opti, or the ecm.
From there, check for voltage going to the coil.
If theres voltage, then it's the coil. If not, then check for voltage coming from the opti at the opti harness.
If there's no voltage, it's the opti, if there's voltage its the ecm.
Now, if the car just dies, as in no warning, no misfire, no otherwise bad behavior, it just quits, I'm going to bet on the icm. The heat sink wears over time, and when these overheat, they simply quit. A bad Fuel pump or regulator will act like it's out of gas and sputter then die. A bad opti could just quit, but typically will miss, backfire, then quit. But it really sounds like yours is heat related. Of course, I reserve my American Right to be wrong.
Thread Starter
Advanced
Joined: Jul 2012
Posts: 70
Likes: 0
http://www.gmtuners.com/OBD1_DTC.htm
H stands for history, as in not current.
16 is system voltage too low
72 is VSS signal circut error
My first suggestion is to check your ICM. It is located just above the coil. It is mounted to the heat sink that the coil is mounted to. It is held in place by two 7 mm bolts and is easily removed. Take it to an auto parts store and they can test it for you. If it tests bad, of course replace it. If it tests good, get some heat sink grease and apply a nice coat on the back and put it back on.
Then...using the spark tester you bought while you were at the parts store, when the car dies, check for spark from the coil.
If you have good spark, check for spark from the coil wire at the opti end.
If you have spark there, check for spark at the plugs.
I there is spark, your issue is fuel.
If there is no spark at the plugs but there is going to the opti, it's the opti.
If you have no spark from the coil, it's either the coil, the opti, or the ecm.
From there, check for voltage going to the coil.
If theres voltage, then it's the coil. If not, then check for voltage coming from the opti at the opti harness.
If there's no voltage, it's the opti, if there's voltage its the ecm.
Now, if the car just dies, as in no warning, no misfire, no otherwise bad behavior, it just quits, I'm going to bet on the icm. The heat sink wears over time, and when these overheat, they simply quit. A bad Fuel pump or regulator will act like it's out of gas and sputter then die. A bad opti could just quit, but typically will miss, backfire, then quit. But it really sounds like yours is heat related. Of course, I reserve my American Right to be wrong.
H stands for history, as in not current.
16 is system voltage too low
72 is VSS signal circut error
My first suggestion is to check your ICM. It is located just above the coil. It is mounted to the heat sink that the coil is mounted to. It is held in place by two 7 mm bolts and is easily removed. Take it to an auto parts store and they can test it for you. If it tests bad, of course replace it. If it tests good, get some heat sink grease and apply a nice coat on the back and put it back on.
Then...using the spark tester you bought while you were at the parts store, when the car dies, check for spark from the coil.
If you have good spark, check for spark from the coil wire at the opti end.
If you have spark there, check for spark at the plugs.
I there is spark, your issue is fuel.
If there is no spark at the plugs but there is going to the opti, it's the opti.
If you have no spark from the coil, it's either the coil, the opti, or the ecm.
From there, check for voltage going to the coil.
If theres voltage, then it's the coil. If not, then check for voltage coming from the opti at the opti harness.
If there's no voltage, it's the opti, if there's voltage its the ecm.
Now, if the car just dies, as in no warning, no misfire, no otherwise bad behavior, it just quits, I'm going to bet on the icm. The heat sink wears over time, and when these overheat, they simply quit. A bad Fuel pump or regulator will act like it's out of gas and sputter then die. A bad opti could just quit, but typically will miss, backfire, then quit. But it really sounds like yours is heat related. Of course, I reserve my American Right to be wrong.
Thanks Again
Le Mans Master
Joined: Dec 2006
Posts: 5,139
Likes: 482
From: H-Town Texas
Ok, so I'm going to take your advice and look at the ICM. I picked up an ICM and Coil today from Advance Auto for $90. I have taken out the ICM and Coil combo (what a pain to get the bracket off), dissembled, and cleaned. I need to pick up some thermal paste tomorrow, then I'll reassemble and hope for the best. I looked at other forums about the ICM failure and their symptoms are very similar to mine. I'm hoping for the best and will keep you updated on what happens tomorrow!
Thanks Again
Thanks Again
Thread Starter
Advanced
Joined: Jul 2012
Posts: 70
Likes: 0
I've got good news: It appears that replacing the ICM and Coil fixed the issue with the car dieing. I drove over 60 miles yesterday without issue 
I also have bad news: After replacing the parts the service engine like keeps coming on and its throwing error 42. Is there something that I didn't install correctly or did I get a defective part? The car runs great now, but it's annoying that the service engine light keeps coming on.
I also have bad news: After replacing the parts the service engine like keeps coming on and its throwing error 42. Is there something that I didn't install correctly or did I get a defective part? The car runs great now, but it's annoying that the service engine light keeps coming on.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Advanced
Joined: Jul 2012
Posts: 70
Likes: 0
Good News: I figured out what was causing the SES light to come on. It was a bad ICM, got another and code 42 went away.
Bad News: Took the car to work this morning and it ran fine. Went to the gym after work(Thank Goodness it's close to home) without issue. When I got into the car to go home, it was giving me problems starting, but started after the third time. It ran for 5 min, then died and I was on the side of the road. Got it started after 20 min of waiting traveled 100 yards to a shopping center where it then cut off again. Had the other two ICM's in the car just in case this happened again. Tried the other two ICM's and it still wouldn't start. Got picked up, ate dinner, came back two hours later to get the car. Car started made it the 1.5 miles to my house and it died in the front of my driveway where it sits now. Hopefully, I'll be able to get it started in an hour and put it back in the garage.
Is this starting to look like the opti-spark?
Bad News: Took the car to work this morning and it ran fine. Went to the gym after work(Thank Goodness it's close to home) without issue. When I got into the car to go home, it was giving me problems starting, but started after the third time. It ran for 5 min, then died and I was on the side of the road. Got it started after 20 min of waiting traveled 100 yards to a shopping center where it then cut off again. Had the other two ICM's in the car just in case this happened again. Tried the other two ICM's and it still wouldn't start. Got picked up, ate dinner, came back two hours later to get the car. Car started made it the 1.5 miles to my house and it died in the front of my driveway where it sits now. Hopefully, I'll be able to get it started in an hour and put it back in the garage.
Is this starting to look like the opti-spark?
Heel & Toe
Joined: Sep 2013
Posts: 16
Likes: 0
Good News: I figured out what was causing the SES light to come on. It was a bad ICM, got another and code 42 went away.
Bad News: Took the car to work this morning and it ran fine. Went to the gym after work(Thank Goodness it's close to home) without issue. When I got into the car to go home, it was giving me problems starting, but started after the third time. It ran for 5 min, then died and I was on the side of the road. Got it started after 20 min of waiting traveled 100 yards to a shopping center where it then cut off again. Had the other two ICM's in the car just in case this happened again. Tried the other two ICM's and it still wouldn't start. Got picked up, ate dinner, came back two hours later to get the car. Car started made it the 1.5 miles to my house and it died in the front of my driveway where it sits now. Hopefully, I'll be able to get it started in an hour and put it back in the garage.
Is this starting to look like the opti-spark?
Bad News: Took the car to work this morning and it ran fine. Went to the gym after work(Thank Goodness it's close to home) without issue. When I got into the car to go home, it was giving me problems starting, but started after the third time. It ran for 5 min, then died and I was on the side of the road. Got it started after 20 min of waiting traveled 100 yards to a shopping center where it then cut off again. Had the other two ICM's in the car just in case this happened again. Tried the other two ICM's and it still wouldn't start. Got picked up, ate dinner, came back two hours later to get the car. Car started made it the 1.5 miles to my house and it died in the front of my driveway where it sits now. Hopefully, I'll be able to get it started in an hour and put it back in the garage.
Is this starting to look like the opti-spark?
Thread Starter
Advanced
Joined: Jul 2012
Posts: 70
Likes: 0
A word on advice that might save you time is to install/test the ICM first, it comes off with two bolts. Hopefully, the new ICM will fix your problem because the coil is a PITA to remove.
Keep me updated, I'll try and help if I can...Best of Luck
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
Thread Starter
Advanced
Joined: Jul 2012
Posts: 70
Likes: 0
Burning Brakes
Joined: Nov 2010
Posts: 855
Likes: 36
From: Crystal Springs MS
I just ordered an opti, wires, and plugs. I've got my fingers crossed this will fix the issue!
A word on advice that might save you time is to install/test the ICM first, it comes off with two bolts. Hopefully, the new ICM will fix your problem because the coil is a PITA to remove.
Keep me updated, I'll try and help if I can...Best of Luck
A word on advice that might save you time is to install/test the ICM first, it comes off with two bolts. Hopefully, the new ICM will fix your problem because the coil is a PITA to remove.
Keep me updated, I'll try and help if I can...Best of Luck
Thread Starter
Advanced
Joined: Jul 2012
Posts: 70
Likes: 0
Heel & Toe
Joined: Sep 2013
Posts: 16
Likes: 0
I just ordered an opti, wires, and plugs. I've got my fingers crossed this will fix the issue!
A word on advice that might save you time is to install/test the ICM first, it comes off with two bolts. Hopefully, the new ICM will fix your problem because the coil is a PITA to remove.
Keep me updated, I'll try and help if I can...Best of Luck
A word on advice that might save you time is to install/test the ICM first, it comes off with two bolts. Hopefully, the new ICM will fix your problem because the coil is a PITA to remove.
Keep me updated, I'll try and help if I can...Best of Luck
Junior Member
Garage is empty, add now
My Corvette Photos
Member Since: Sep 2013
I changed the ICM and it ran great for twenty minutes,then I parked it for two hours, tried to start it and wouldn't start. Put the jumper on and got only one code, H72 - gear shift selector circuit?? Anyone have any ideas??
Thread Starter
Advanced
Joined: Jul 2012
Posts: 70
Likes: 0
Dalu
Junior Member
Garage is empty, add now
My Corvette Photos
Member Since: Sep 2013
I changed the ICM and it ran great for twenty minutes,then I parked it for two hours, tried to start it and wouldn't start. Put the jumper on and got only one code, H72 - gear shift selector circuit?? Anyone have any ideas??
Junior Member
Garage is empty, add now
My Corvette Photos
Member Since: Sep 2013
I changed the ICM and it ran great for twenty minutes,then I parked it for two hours, tried to start it and wouldn't start. Put the jumper on and got only one code, H72 - gear shift selector circuit?? Anyone have any ideas??
Last edited by pushing255; Sep 22, 2013 at 06:59 PM.
Safety Car
Joined: Jun 2003
Posts: 4,250
Likes: 656
From: San Diego Ca
I haven't found the opti to be an intermittent problem either. It either is good or bad. Now all the connectors and sensors could be bad, but I am not liking the Opti as the culprit here. If you are driving around with 3 ICMs than what is causing them to suddenly decide to quit working?
I don't have an answer for you but I would start thinking along that line of inquiry.
I don't have an answer for you but I would start thinking along that line of inquiry.
Heel & Toe
Joined: Sep 2013
Posts: 16
Likes: 0
Burning Brakes
Joined: Nov 2010
Posts: 855
Likes: 36
From: Crystal Springs MS
I haven't found the opti to be an intermittent problem either. It either is good or bad. Now all the connectors and sensors could be bad, but I am not liking the Opti as the culprit here. If you are driving around with 3 ICMs than what is causing them to suddenly decide to quit working?
I don't have an answer for you but I would start thinking along that line of inquiry.
I don't have an answer for you but I would start thinking along that line of inquiry.