93 with no injector pulse
Thread Starter
Intermediate
Joined: Jul 2012
Posts: 29
Likes: 1
From: Fort Myers Florida
93 with no injector pulse
I have a 93 with no injector pulse using a noid light. The fuel pressure is good, and it has spark, (if I spray carb cleaner in the TB it runs). I get "no communication" from my monitor so I can't check codes. It has been running fine, I parked it in my drive went to put it in the garage and it fires just for a split second the quits. If someone has any input as to what it could be, opti, ECM, VATS. The ICM is nearly new and the opti is the original w/mitsu module. thanks in advance.
Race Director
Joined: Oct 2011
Posts: 16,086
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From: Dallas Texas
2025 C4 of the Year Finalist - Modified
If I recall correctly, when my opti died on my first '93 C4, I was getting spark, but the injectors weren't pulsating. I might get called out on this tho 
Race Director
Joined: Apr 2002
Posts: 10,036
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From: Anaheim CA
The ECM uses reference pulses from the opti (through the ignition module) to know when to fire the injectors. It does this to synchronize the firing of the injectors to the rotation of the engine. It appears that this reference signal is not getting to the ECM. Check the connectors (corroded pins?) and wiring related to this connection.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
I do not believe the opti is bad or the problem. If you have spark, then the low resolution reference pulse is reaching the ECM. Without the pulse there would be no spark either.
So going on the assumption the opti is OK, look to the injector circuits. Make sure that is 12 volts on each pin of all the injectors. Voltage comes from 2 fuses one for each side. Both sides of each injector pins should have 12 volts on it (with engine not running). If this is OK, and there is spark the ECM could be the problem.
However the larger item that bothers me is that you cannot get any codes. This could be a communication problem with the CCM. And if the CCM is not working properly, then the signal (or bus handshake) pulse to turn on the ECM for the injectors might be missing. This is the FEDS part of the anti-thief system and does require the CCM to be healthy.
Make sure all CCM fuses are good and look for any corrosion. Any bad connection to inhibit the CCM from working will cause this problem.
I would check out other functions of the CCM like interior lights and other related functions.
So going on the assumption the opti is OK, look to the injector circuits. Make sure that is 12 volts on each pin of all the injectors. Voltage comes from 2 fuses one for each side. Both sides of each injector pins should have 12 volts on it (with engine not running). If this is OK, and there is spark the ECM could be the problem.
However the larger item that bothers me is that you cannot get any codes. This could be a communication problem with the CCM. And if the CCM is not working properly, then the signal (or bus handshake) pulse to turn on the ECM for the injectors might be missing. This is the FEDS part of the anti-thief system and does require the CCM to be healthy.
Make sure all CCM fuses are good and look for any corrosion. Any bad connection to inhibit the CCM from working will cause this problem.
I would check out other functions of the CCM like interior lights and other related functions.
Last edited by pcolt94; Dec 3, 2014 at 12:56 PM.
Instructor
Joined: Sep 2004
Posts: 208
Likes: 1
From: Lawrenceville GA
Speaking from experience, You can bypass the ccm signal by way of the ecm eprom. Either have the eprom reflashed or PCM of NC sells a piggyback eprom. I had to bypass Passkey and VATS plus the opti last spring.
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
Check the two fuel injector fuses, if either or both are blown then check the resistance value of each injector as one could be shorted which blew the fuse.
But sounds like the ECM is gone as there is no communications from it. I seem to remember that the '93 ECM is difficult to find.
Good luck.
But sounds like the ECM is gone as there is no communications from it. I seem to remember that the '93 ECM is difficult to find.
Good luck.
Thread Starter
Intermediate
Joined: Jul 2012
Posts: 29
Likes: 1
From: Fort Myers Florida
Thanks for all the help. It's been a week now and I still haven't gotten anywhere. I Ohm checked all the injectors (15 Ohms on all), checked for any bad grounds and checked all the fuses. I replace the ICM with one I had just in case, still no injector pulse. On occasion it will fire for a second maybe 1 revolution but that's it. I double checked my Snap-On monitor and I still can't get communication, that's what really bothers me. The CCM, is that located inside the car near the radio? I hopefully will get some time this weekend to work on it, and I'll post what I find when I find it. At least it died (no start) in the driveway! Keep the suggestion/tips coming I appreciate it.
Thanks,
Ron
Thanks,
Ron
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Melting Slicks
Joined: Aug 1999
Posts: 2,240
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From: Baltimore, MD USA
You don't need a code reader to communicate with the ECM.
Use a piece of wire and short pin A to pin G on the diag. connector.
Turn the ignition On and look at the speedometer LCD.
Module 1 is the CCM
Module 4 is the ECM
If you get ERR for module 4 it indicates the CCM can not communicate
with the ECM.
If that happens, turn the ignition off and short pin A to pin B.
Turn the ignition On and look at the Service Engine Soon indicator.
It should blink 12 three times any codes three times and at the end of the sequence blink 12 again three times.
Example. 12 would be flash pause flash, flash long pause then 12 again.
If this fails something is wrong with the ECM and you need to verify 12 volts and ground at the ECM connectors.
Use a piece of wire and short pin A to pin G on the diag. connector.
Turn the ignition On and look at the speedometer LCD.
Module 1 is the CCM
Module 4 is the ECM
If you get ERR for module 4 it indicates the CCM can not communicate
with the ECM.
If that happens, turn the ignition off and short pin A to pin B.
Turn the ignition On and look at the Service Engine Soon indicator.
It should blink 12 three times any codes three times and at the end of the sequence blink 12 again three times.
Example. 12 would be flash pause flash, flash long pause then 12 again.
If this fails something is wrong with the ECM and you need to verify 12 volts and ground at the ECM connectors.
Thread Starter
Intermediate
Joined: Jul 2012
Posts: 29
Likes: 1
From: Fort Myers Florida
OK, so I had some time today to run some more tests. I have 12V on all the injector leads, (key on) all the fuses check good, interior lights all function. I have found absolutly no visable signs of corrosion anywhere, so I assuming thats not the problem. I took Hooked on Vettes advice and ran codes the "paper clip" way. When I short A to G I get this sequence, C41 - H41 - Err - H64 - H72. When I short A to B I get code 26, which seems to be an EGR, canister purge, air pump code, which is probably not causing my problem. If anyone has any insight as to where to go next, please chime in. Thanks for all the help.
Ron
Ron
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
OK, so I had some time today to run some more tests. I have 12V on all the injector leads, (key on) all the fuses check good, interior lights all function. I have found absolutly no visable signs of corrosion anywhere, so I assuming thats not the problem. I took Hooked on Vettes advice and ran codes the "paper clip" way. When I short A to G I get this sequence, C41 - H41 - Err - H64 - H72. When I short A to B I get code 26, which seems to be an EGR, canister purge, air pump code, which is probably not causing my problem. If anyone has any insight as to where to go next, please chime in. Thanks for all the help.
Ron
Ron
Module 1 DTC 41 indicates the CCM can not communicate with the ECM and disables FEDS so there will be no injector pulsing.
Module 9 DTC 72 indicates the CCM can not communicate with the EBTCM computer located in the rear storage bin behind the drivers seat.
The CCM communicates with the EBTCM, C68 Programmer and the ECM by the serial bus. (serial bus is a piece of wire going to each module).
Disconnect the negative battery terminal.
Unplug the Brown connector at the ECM.
This removes the ECM from the serial bus.
Reconnect the negative battery terminal and short pin A to G.
Turn the ignition On. Verify if you still get a DTC 72 for Module 9.
If you don't, that indicates the ECM is causing the problem with the serial bus.
If you still get DTC 72 for Module 9.
Disconnect the negative battery cable. Remove the connector going to the EBTCM and reconnect the Brown ECM connector. Reconnect the battery and verify if Module 1 DTC 41 is gone. If it is the EBTCM is bad and the engine should start.
Last edited by Hooked on Vettes; Dec 6, 2014 at 07:12 PM.
Thread Starter
Intermediate
Joined: Jul 2012
Posts: 29
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From: Fort Myers Florida
I know this thread is long in the tooth but I've been working on diagnosing my problem all this time and I said I would post when I fixed it. I thought someone may benifit in some small way from my issues. I finally fixed it, it was the ECM. I suspected it all along but I wanted to eliminate all other possibilities. I picked up a used one on Fleabay for $65.00, and it fired right up. Thanks to all who replied and helped me narrow down my target components.
Ron
Ron
Race Director
Joined: Oct 2011
Posts: 16,086
Likes: 819
From: Dallas Texas
2025 C4 of the Year Finalist - Modified
I know this thread is long in the tooth but I've been working on diagnosing my problem all this time and I said I would post when I fixed it. I thought someone may benifit in some small way from my issues. I finally fixed it, it was the ECM. I suspected it all along but I wanted to eliminate all other possibilities. I picked up a used one on Fleabay for $65.00, and it fired right up. Thanks to all who replied and helped me narrow down my target components.
Ron
Ron
Advanced
Joined: Sep 2014
Posts: 82
Likes: 0
I have a 93 with no injector pulse using a noid light. The fuel pressure is good, and it has spark, (if I spray carb cleaner in the TB it runs). I get "no communication" from my monitor so I can't check codes. It has been running fine, I parked it in my drive went to put it in the garage and it fires just for a split second the quits. If someone has any input as to what it could be, opti, ECM, VATS. The ICM is nearly new and the opti is the original w/mitsu module. thanks in advance.
