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I have a 1998 C5 auto. I have been getting intermittent issues when trying to start. I have changed the starter, it was original, put in a new ignition switch and a new TDR.
Now for the TDR I am getting 12v to the red wire, 12 volts to the yellow from the ignition when I try to start, no voltage to the purple and for
some reason the yellow and black wire is giving me 12 volts instead of a ground when I try to start. If I jump the red and purple the engine spins or may start but then immediately dies.
Verify if the Body Control Module ground the A1 side of the TDR relay.
The 12 volt measured on A1 of the TDR or the B7:C3 shall go from 12 volt to 0.1-0.2 volt when TDR energize IF the ground path of the BCM is okay
Measure voltage between TDR terminal A2 and a groundpoint .
When you press ignitionswitch to start the the relay should close contact between C1 -A2 if the relay is okay the 12volt on the red wire shall be connected to purple wire .
Since your car start when you jump RED and PUPLE wire the relay who is supposed this does not operating correct .
Maybe because of the relay or due to groundpath for TDR relay activating is not good ( voltage drops in groundloop)
I tested this on my car last year how the and I measured 0 volt and you seems to measure 0.36 volt and I am not sure your ground connection is 100% good.
If you set ignition key in ON and then in a short moment connect a ground wire to A1(yellow/black) the TDR should activate and your starter should spin a sesond if the relay is okay .
If the car start now , check the ground wire loop. The pictore below show a splicepoint causing similar problems to other people
Hope this info help
I tested A2 (the purple wire) and got 0 volts. I tried that with the key on and in the start position and I still get 0 volts at A2 purple.
I grounded A1 (the yellow/black wire) to the negative post on the battery, turned the key to start and then the engine spins, starts for second and then dies.
To me it looks like the TDR relay activate and when you add an extra ground path to A1 term of the TDR relay .
I think the BCM is not grounding the A1 properly as it should .
Remove the TDR relay and put one meter lead in the A1 (black/yellow) and the other lead to a grounding point (I used passenger doorstep nearby)
The Meter is set to resistance measurement . When you move the ignitionkey to start the restistance shall change from a high value (I measured 3 M ohm) to zero ohm.
I measured values shown below when I verified this last year on my own car .
Please report back your restistance values , If the value does not drops to zero by the BodyControl Module this may be your problem .
C5 will not start
