No Codes from ECM
Thread Starter
7th Gear
Joined: Jul 2006
Posts: 7
Likes: 0
No Codes from ECM
Please refer also to my 88 corvette starting and running problems..
Tried to get codes today by jumping A and B (top right two) My understand is that the Service engine light should start blinking and give a code 12 to start with to verify it is able to communicate. My Service engine light stays on and will not blink at all. Book says if this happens, needs to be checked by pro. I also have a radiator fan motor running all the time when ign switch is on even though ac if off, engine is cold, and temp reads lo on dash. Also have almost no gas pressure at manifold but when fuel pump relay is jumped, plenty of pressure.
Is my ECM bad???
Thanks
Wayne
Tried to get codes today by jumping A and B (top right two) My understand is that the Service engine light should start blinking and give a code 12 to start with to verify it is able to communicate. My Service engine light stays on and will not blink at all. Book says if this happens, needs to be checked by pro. I also have a radiator fan motor running all the time when ign switch is on even though ac if off, engine is cold, and temp reads lo on dash. Also have almost no gas pressure at manifold but when fuel pump relay is jumped, plenty of pressure.
Is my ECM bad???
Thanks
Wayne
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by Sealawyer5
Please refer also to my 88 corvette starting and running problems..
Tried to get codes today by jumping A and B (top right two) My understand is that the Service engine light should start blinking and give a code 12 to start with to verify it is able to communicate. My Service engine light stays on and will not blink at all. Book says if this happens, needs to be checked by pro. I also have a radiator fan motor running all the time when ign switch is on even though ac if off, engine is cold, and temp reads lo on dash. Also have almost no gas pressure at manifold but when fuel pump relay is jumped, plenty of pressure.
Is my ECM bad???
Thanks
Wayne
Tried to get codes today by jumping A and B (top right two) My understand is that the Service engine light should start blinking and give a code 12 to start with to verify it is able to communicate. My Service engine light stays on and will not blink at all. Book says if this happens, needs to be checked by pro. I also have a radiator fan motor running all the time when ign switch is on even though ac if off, engine is cold, and temp reads lo on dash. Also have almost no gas pressure at manifold but when fuel pump relay is jumped, plenty of pressure.
Is my ECM bad???
Thanks
Wayne
Disconnect both ECM connetors under the dash and turn the ignition on (not grounding A and B). If the light is on repair the short in circuit 419 (it's the wire that goes to the SES light). If the light is off reconnect the ECM connectors and back probe circuit 451 with the ignition on. If the code 12 flashes there is and open in one of the ALDL A or B circuits. If no code 12 check to make sure the MEM-CAL is installed properly, if you have messed with it.
EDIT: the ECM is probably o.k. and just needs to be checked with a test light to make sure. When the SES light flashes a code 12 this is showing that the diagnostic check in the ECM is good. I figure it is a bad ground or loose connection in one of the two circuits described above. The fuel pump relay sounds bad if you can jump the first and last wire on the connector and the system primes. I would suggest first to check the ECM circuits out and then once it is working again, then check the FP relay. Does the engine start and run properly?
Last edited by RRT vette; Jul 9, 2006 at 07:38 AM.
Thread Starter
7th Gear
Joined: Jul 2006
Posts: 7
Likes: 0
Engine will only run about one or two seconds. This is usuell in the mornings when my garage is well below the 100 deg cold start cut out.
The radiator fan runs and has been running (when ign switch on) since I noticed it wouldn't stay running, long before I tried to jump a and b.
Yesterday after I cleaned and cleaned the key cylinder, it was so hot in the garage, it wouldn't crank at all. I'm thinking the cold start is not controled by the ecm. It was about 120 or so in the garage all afternoon. Does the ecm determine when to turn the fuel pump off? I know it runs when ign is turned on but never runs long enough to get pressure to the injector manifold. When I jumped out the relay, I had pressure. I didn;t have a guage but could tell by the spray, it was pretty good.
Wayne
The radiator fan runs and has been running (when ign switch on) since I noticed it wouldn't stay running, long before I tried to jump a and b.
Yesterday after I cleaned and cleaned the key cylinder, it was so hot in the garage, it wouldn't crank at all. I'm thinking the cold start is not controled by the ecm. It was about 120 or so in the garage all afternoon. Does the ecm determine when to turn the fuel pump off? I know it runs when ign is turned on but never runs long enough to get pressure to the injector manifold. When I jumped out the relay, I had pressure. I didn;t have a guage but could tell by the spray, it was pretty good.
Wayne
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by Sealawyer5
Engine will only run about one or two seconds. This is usuell in the mornings when my garage is well below the 100 deg cold start cut out.
The radiator fan runs and has been running (when ign switch on) since I noticed it wouldn't stay running, long before I tried to jump a and b.
Yesterday after I cleaned and cleaned the key cylinder, it was so hot in the garage, it wouldn't crank at all. I'm thinking the cold start is not controled by the ecm. It was about 120 or so in the garage all afternoon. Does the ecm determine when to turn the fuel pump off? I know it runs when ign is turned on but never runs long enough to get pressure to the injector manifold. When I jumped out the relay, I had pressure. I didn;t have a guage but could tell by the spray, it was pretty good.
Wayne
The radiator fan runs and has been running (when ign switch on) since I noticed it wouldn't stay running, long before I tried to jump a and b.
Yesterday after I cleaned and cleaned the key cylinder, it was so hot in the garage, it wouldn't crank at all. I'm thinking the cold start is not controled by the ecm. It was about 120 or so in the garage all afternoon. Does the ecm determine when to turn the fuel pump off? I know it runs when ign is turned on but never runs long enough to get pressure to the injector manifold. When I jumped out the relay, I had pressure. I didn;t have a guage but could tell by the spray, it was pretty good.
Wayne
"it wouldn't crank at all"...as in you turn the key and nothing, not even a sound?
The CSV is controlled by a fuse and switch. The power for it comes from the starter solenoid. The fuse #5 is located behind the DIC where the SES light is. The switch is located on the front of the intake manifold near the CTS. Correct, in no way does the ECM control the CSV, and the thermal time switch cuts the CSV off appropriately as the engine temp increases.
When the ignition is turned to the on position the fuel pump relay sends the signal to the fuse panel, then to the pump and only for two seconds. If you can jumper the FP relay harness and the pump runs then I would think you have a bad fuel pump relay, but fix the open/grounded circuit first.
Thread Starter
7th Gear
Joined: Jul 2006
Posts: 7
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Thanks everyone...
Problem Solved... Replaced ECM
Fan operates normal, Fuel pressure good, Engine cranks and runs great.
Thanks Wayne
Note: I think this was going bad for some time because I can't remember the car running this tight. overdrive shifts perfect and power is now awsome. 4+3 tranny
Problem Solved... Replaced ECM
Fan operates normal, Fuel pressure good, Engine cranks and runs great.
Thanks Wayne
Note: I think this was going bad for some time because I can't remember the car running this tight. overdrive shifts perfect and power is now awsome. 4+3 tranny
