CAR ISSUES : 93 camaro z28 lt1
02-17-2011, 12:12 PM
#1
Teching In
Thread Starter
Join Date: Feb 2011
Posts: 44
Likes: 0
Received 0 Likes
on
0 Posts
CAR ISSUES : 93 camaro z28 lt1 RamAir95TA : K, performed a jumper and ECM looks to be good (Check engine light off). Thing is following DTC code 12, the SES light will indicate a diagnostic trouble code three times if a code is present or it will continue to flash DTC 12. This one continues to flash DTC 12.
Problem with the car though,
Once on..idles good on Park but, when shifted to Drive thats when the car like bogs down and turns off. Smells lots of fuel. Car also smokes alittle from exaust.
This is the reason why my mechanic worries. He wants to know if ECM not picking up any codes, why is it that car stalls and turns off when shifted to Drive.
Any suggestions ?
Problem with the car though,
Once on..idles good on Park but, when shifted to Drive thats when the car like bogs down and turns off. Smells lots of fuel. Car also smokes alittle from exaust.
This is the reason why my mechanic worries. He wants to know if ECM not picking up any codes, why is it that car stalls and turns off when shifted to Drive.
Any suggestions ?
02-17-2011, 12:37 PM
#2
DTC - 12 No distributor reference pulse (diagnostic test active)
Start with this
From Shbox website
Disconnect the ICM connector. Leave coil connected.
Turn key to ON.
Check for dc voltage with a digital meter at harness terminal "A" to ground and and also "D" to ground. Note: Use a high impedance meter (at least 10 megohm) when dealing with the PCM.
Result should be 10v dc or more on both terminals. If you get no voltage, use the diagram and chase back toward the coil and the ignition fuse. Power for the ICM comes from the ignition fuse and through the coil, so any of that could be bad.
If you have good voltage, switch the meter to ac scale and connect test leads to terminal "B" and to ground. Observe meter while cranking the engine. You should see between 1 and 4 volts ac (those are the pulses that trigger the coil to fire).
If you don't see the proper ac voltage the problem could be the optispark, the harness to the optispark, the PCM or any of the wiring in between. Visually inspect all the connections you can get to for poor contact or corrosion.
Start with this
From Shbox website
Disconnect the ICM connector. Leave coil connected.
Turn key to ON.
Check for dc voltage with a digital meter at harness terminal "A" to ground and and also "D" to ground. Note: Use a high impedance meter (at least 10 megohm) when dealing with the PCM.
Result should be 10v dc or more on both terminals. If you get no voltage, use the diagram and chase back toward the coil and the ignition fuse. Power for the ICM comes from the ignition fuse and through the coil, so any of that could be bad.
If you have good voltage, switch the meter to ac scale and connect test leads to terminal "B" and to ground. Observe meter while cranking the engine. You should see between 1 and 4 volts ac (those are the pulses that trigger the coil to fire).
If you don't see the proper ac voltage the problem could be the optispark, the harness to the optispark, the PCM or any of the wiring in between. Visually inspect all the connections you can get to for poor contact or corrosion.
02-17-2011, 01:20 PM
#3
OP has a 93 car, ECM with PROM chip, unlike the surface-mounted EEPROM (erasable/programmable) PCM in 94 & up. OBDI PROM cars do a code 12, which simply means the ECM has entered diagnostic mode. If there are no codes between the preamble code 12 and the final code 12, there are no stored codes. There could have been, but if the battery has been disconnected and they've been thusly cleared, they'll need to show up again by running the car into closed loop (let it run in park until it warms up, maybe twice). Any codes that were stored earlier should reappear.
It's also possible you have a big vacuum leak somewhere. Try to eliminate mechanical sources of trouble before digging in too deep elsewhere. Also, look at the cabling on the trans for kinks on the throttle valve cable, etc. to make sure nothing is hung up and causing the trans to bog & kill the engine. Google "700r4 vacuum diagram" for help on eliminating the trans issues as well.
It's also possible you have a big vacuum leak somewhere. Try to eliminate mechanical sources of trouble before digging in too deep elsewhere. Also, look at the cabling on the trans for kinks on the throttle valve cable, etc. to make sure nothing is hung up and causing the trans to bog & kill the engine. Google "700r4 vacuum diagram" for help on eliminating the trans issues as well.
Last edited by Gojira94; 02-18-2011 at 08:29 AM.
02-17-2011, 03:28 PM
#4
OP has a 93 car, ECM with PROM chip, unlike the surface-mounted EEPROM (erasable/programmable) PCM in 94 & up. OBDI PROM cars do a code 12, which simply means the ECM has entered diagnostic mode. Not the same code 12 as above. If there are no codes between the preamble code 12 and the final code 12, there are no stored codes. There could have been, but if the battery has been disconnected and they've been thusly cleared, they'll need to show up again by running the car into closed loop (let it run in park until it warms up, maybe twice). Any codes that were stored earlier should reappear.
It's also possible you have a big vacuum leak somewhere. Try to eliminate mechanical sources of trouble before digging in too deep elsewhere. Also, look at the cabling on the trans for kinks on the throttle valve cable, etc. to make sure nothing is hung up and causing the trans to bog & kill the engine. Google "700r4 vacuum diagram" for help on eliminating the trans issues as well.
It's also possible you have a big vacuum leak somewhere. Try to eliminate mechanical sources of trouble before digging in too deep elsewhere. Also, look at the cabling on the trans for kinks on the throttle valve cable, etc. to make sure nothing is hung up and causing the trans to bog & kill the engine. Google "700r4 vacuum diagram" for help on eliminating the trans issues as well.
02-18-2011, 08:28 AM
#5
A code 12 in this case just indicates that the ECM is not getting pulses from the distributor, simply because the engine isn't running. If you scan for codes with a scanner with the engine running, you won't see a code 12.
You sure you didn't have a code 16? That's common, low resolution pulses not getting to the ECM/ PCM
You sure you didn't have a code 16? That's common, low resolution pulses not getting to the ECM/ PCM
02-19-2011, 01:12 AM
#7
The 4l60(700R4) uses a detent (throttle valve) cable, and a governor. There is no vacuum control on the trans. If it's happening while the car is cold (running in closed loop), it may be a lack of spark energy, and loading up with fuel. I'd try checking the coil, ICM, and fuel pressure both in Park and in gear to verify if the vacuum control on the fuel pressure regulator is working.
