86 wiring harness/ECM code question
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86 wiring harness/ECM code question
I have an 86 C4 that I have finished doing a total rebuild on, new engine, transmission and replacement wiring harness from an 87. I have cleaned and rechecked all leads, grounds and connectors and have bought a new battery. when I try to start the car the security light comes on with the door open and the key out, but it goes out when the door is shut. when the key is inserted and turned on the service engine light comes on and all the dash lights work but the starter will not engage. I have done a non scan check and all I get for codes is a repeating 12 and no others. I have done the key resistance on both keys and get 7.17 and 7.37 and done the bypass on the connector on the column with resistors of 7.07k and still the same no start. I have been looking at vats sucks site and may need to reprogram the chip but would like some ideas first. If I do the chip I guess I would still have to disable the start enable relay, but w/o any codes I am not sure this is a VATS issue. any ideas would be appreciated. the car started fine w/o any problems before pulling the engine and wiring harness about two years ago and nothing has been changed other than the harness.
Last edited by merrillgtrs; Feb 2, 2015 at 04:03 PM.
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From: Anaheim CA
The SECURITY light is part of the UTD (Universal Theft Deterrent) system, usually known as TDS (Theft Deterrent System). All it does is honk the horn if the door is opened while the system is armed. There is no connection to VATS or the ECM.
The SECURITY light flashes when the door is open and the system is NOT armed. That's a reminder to arm the system (by locking the door) before closing the door.
The SECURITY light will stay on solid if the TDS system is armed and the door is open.
The SECURITY light will go out if you close the door or turn on the ignition.
When you turn the key cylinder to the start position you should hear the starter enable relay click. It is located behind the DIC (Driver Information Center) in the center cluster. That relay is controlled by the VATS system in 1986 and later cars (the TDS system controlled it in earlier cars). You can bypass the starter enable relay like so:
If the ECM fails to detect the signal from the VATS system it will set error code 46. That signal is only tested when the ignition is first turned on, so you do not need to crank the engine to get the VATS signal to the ECM (or not).
You should check to see if 12 volts is getting to the starter solenoid. The positive battery cable connects directly to the starter solenoid and you should get 12 volts on the other wire when the ignition cylinder is turned to the start position.
The SECURITY light flashes when the door is open and the system is NOT armed. That's a reminder to arm the system (by locking the door) before closing the door.
The SECURITY light will stay on solid if the TDS system is armed and the door is open.
The SECURITY light will go out if you close the door or turn on the ignition.
When you turn the key cylinder to the start position you should hear the starter enable relay click. It is located behind the DIC (Driver Information Center) in the center cluster. That relay is controlled by the VATS system in 1986 and later cars (the TDS system controlled it in earlier cars). You can bypass the starter enable relay like so:
If the ECM fails to detect the signal from the VATS system it will set error code 46. That signal is only tested when the ignition is first turned on, so you do not need to crank the engine to get the VATS signal to the ECM (or not).
You should check to see if 12 volts is getting to the starter solenoid. The positive battery cable connects directly to the starter solenoid and you should get 12 volts on the other wire when the ignition cylinder is turned to the start position.
Last edited by Cliff Harris; Feb 3, 2015 at 01:05 AM.
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still no start
[QUOTE=Cliff Harris;1588871754]The SECURITY light is part of the UTD (Universal Theft Deterrent) system, usually known as TDS (Theft Deterrent System). All it does is honk the horn if the door is opened while the system is armed. There is no connection to VATS or the ECM.
The SECURITY light flashes when the door is open and the system is NOT armed. That's a reminder to arm the system (by locking the door) before closing the door.
The SECURITY light will stay on solid if the TDS system is armed and the door is open.
The SECURITY light will go out if you close the door or turn on the ignition.
When you turn the key cylinder to the start position you should hear the starter enable relay click. It is located behind the DIC (Driver Information Center) in the center cluster. That relay is controlled by the VATS system in 1986 and later cars (the TDS system controlled it in earlier cars). You can bypass the starter enable relay like so:
If the ECM fails to detect the signal from the VATS system it will set error code 46. That signal is only tested when the ignition is first turned on, so you do not need to crank the engine to get the VATS signal to the ECM (or not).
You should check to see if 12 volts is getting to the starter solenoid. The positive battery cable connects directly to the starter solenoid and you should get 12 volts on the other wire when the ignition cylinder is turned to the start position.[/QUOTE
thanks for the continuing help on this issue.
I have made up a resistor bypass of 7.07 for the connector on the steering column, my keys read 7.17 and 7.33.
I have done the starter enable relay bypass you showed in your last post.
with the resistor set up in or out and the starter enable bypass in I still get a service engine soon light on the dash and no starter engage at all. I have also waited the four plus minutes for the reset mentioned and no difference unless I have not waited long enough.
I have checked the starter solenoid with the key on and get a 12 volt plus reading and have rechecked everything that I can think of as to grounds and connections from when I installed the newer wiring harness along with the engine rebuild on this car.
I do get sounds out of the
ECM now that I did not get before and have checked and removed and replaced the leads to the ECM. there is a difference on the two harness connectors to the ECM, the car being an 86 and the old harness having blue and grey plastic inserts and metal clips along the sides whereas the 87 replacement harness has actual clips on the harness that go onto the computer if that makes any difference. I cannot see where the older pieces can go on the newer harness set up and the connections seem to be tight. the ECM was replaced on this car within the last 2-3k miles of me buying it but the invoice I have from that has no info as to what was done other than the replacement of the ECM itself. the car did start ok when I got it but needed a complete engine rebuild and harness replacement which is how I got to here.
The SECURITY light flashes when the door is open and the system is NOT armed. That's a reminder to arm the system (by locking the door) before closing the door.
The SECURITY light will stay on solid if the TDS system is armed and the door is open.
The SECURITY light will go out if you close the door or turn on the ignition.
When you turn the key cylinder to the start position you should hear the starter enable relay click. It is located behind the DIC (Driver Information Center) in the center cluster. That relay is controlled by the VATS system in 1986 and later cars (the TDS system controlled it in earlier cars). You can bypass the starter enable relay like so:
If the ECM fails to detect the signal from the VATS system it will set error code 46. That signal is only tested when the ignition is first turned on, so you do not need to crank the engine to get the VATS signal to the ECM (or not).
You should check to see if 12 volts is getting to the starter solenoid. The positive battery cable connects directly to the starter solenoid and you should get 12 volts on the other wire when the ignition cylinder is turned to the start position.[/QUOTE
thanks for the continuing help on this issue.
I have made up a resistor bypass of 7.07 for the connector on the steering column, my keys read 7.17 and 7.33.
I have done the starter enable relay bypass you showed in your last post.
with the resistor set up in or out and the starter enable bypass in I still get a service engine soon light on the dash and no starter engage at all. I have also waited the four plus minutes for the reset mentioned and no difference unless I have not waited long enough.
I have checked the starter solenoid with the key on and get a 12 volt plus reading and have rechecked everything that I can think of as to grounds and connections from when I installed the newer wiring harness along with the engine rebuild on this car.
I do get sounds out of the
ECM now that I did not get before and have checked and removed and replaced the leads to the ECM. there is a difference on the two harness connectors to the ECM, the car being an 86 and the old harness having blue and grey plastic inserts and metal clips along the sides whereas the 87 replacement harness has actual clips on the harness that go onto the computer if that makes any difference. I cannot see where the older pieces can go on the newer harness set up and the connections seem to be tight. the ECM was replaced on this car within the last 2-3k miles of me buying it but the invoice I have from that has no info as to what was done other than the replacement of the ECM itself. the car did start ok when I got it but needed a complete engine rebuild and harness replacement which is how I got to here.
