HELP! Theft deterrent relay location
Melting Slicks
Joined: Sep 2008
Posts: 3,138
Likes: 802
From: Espanola New Mexico
I will post this final reply in the hope that you can figure out how the starting circuit works. 12v is supplied to the Ignition switch and power is supplied to the various systems that are needed to start the car. When the key is inserted and turned to the run position contacts on the very front of the Ignition switch press against the keys resistor pellet, there are two black wires with a connector that are connected to those contacts. The two wires are wired to a connector at the BCM, the BCM recognizes the keys resistor value as the correct one and provides a ground to one side of the TDR relay coil. The 12v from the Ignition switch start contacts makes its way to either the Park/Neutral switch if auto, or to the clutch safety switch and then is applied to the other side of the TDR coil. The TDR when energized then closes its contacts and sends power to the starter solenoid.
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Instructor
Joined: Dec 2022
Posts: 193
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From: St. Louis Missouri
I have an excellent shop. They work on all years makes and models. Lots of hot rods and vintage cars there. Very capable of fixing this. I just want to fix it myself. Seems like I should
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Instructor
Joined: Dec 2022
Posts: 193
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From: St. Louis Missouri
I appreciate everyone trying to help me out. mmartinez made it as simple as it gets.
i have zero experience with electrical systems so trying to figure it out may take a while. Was expecting to change the oil and do a starter or water pump myself but this was a bit much. I’ll probably just take it to the shop and get it done right before I break something else.
thanks for the input!!
i have zero experience with electrical systems so trying to figure it out may take a while. Was expecting to change the oil and do a starter or water pump myself but this was a bit much. I’ll probably just take it to the shop and get it done right before I break something else.
thanks for the input!!
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Heel & Toe
Joined: May 2024
Posts: 15
Likes: 1
You can clip on to the yellow wire and a ground to check for 12v when the key is turned to the start position. This test will tell you that 12v is leaving the Ignition switch going thru the Park/Neutral or clutch safety switch if it's a 6 speed manual The second measurement is clipping the meter lead to the yellow black stripped and the supply side of a fuse in the fuse box, you should see 12v when the key in the on position. Verify which test does not show 12v and we can proceed from there.
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
If you are not seeing 12 volts at the TDR relay either the clutch pedal or park/neutral switch is bad…just follow the purple wire out of the IP Fusebox…if the yellow wire at the TDR is getting 12 volts the coil side of the TDR relay will energize once the BCM grounds the “Relay Control” circuit…once that happens the “load” side of the TDR relay will close allowing power to energize the starter solenoid.
Heel & Toe
Joined: May 2024
Posts: 15
Likes: 1
If you are not seeing 12 volts at the TDR relay either the clutch pedal or park/neutral switch is bad…just follow the purple wire out of the IP Fusebox…if the yellow wire at the TDR is getting 12 volts the coil side of the TDR relay will energize once the BCM grounds the “Relay Control” circuit…once that happens the “load” side of the TDR relay will close allowing power to energize the starter solenoid.
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
If you think the ignition switch is bad place one lead of your voltmeter on either test point on fuse 50 (Ignition 2) and the other lead on fuse 14 (crank) at the IP Fusebox…have someone try to start the engine…whatever your voltmeter reads is the voltage drop across the ignition switch…if you are only seeing 1 volt at the starter purple wire you should expect to see 11 volts on the voltmeter…that voltmeter reading is the voltage drop across the switch…if you see a minus sign on your voltmeter don’t worry about that…just look at the number…if seeing a minus just means you have to switch the leads around…you may also have high resistance on either the clutch or park/neutral switch.
Heel & Toe
Joined: May 2024
Posts: 15
Likes: 1
You can clip on to the yellow wire and a ground to check for 12v when the key is turned to the start position. This test will tell you that 12v is leaving the Ignition switch going thru the Park/Neutral or clutch safety switch if it's a 6 speed manual The second measurement is clipping the meter lead to the yellow black stripped and the supply side of a fuse in the fuse box, you should see 12v when the key in the on position. Verify which test does not show 12v and we can proceed from there.
Heel & Toe
Joined: May 2024
Posts: 15
Likes: 1
If you think the ignition switch is bad place one lead of your voltmeter on either test point on fuse 50 (Ignition 2) and the other lead on fuse 14 (crank) at the IP Fusebox…have someone try to start the engine…whatever your voltmeter reads is the voltage drop across the ignition switch…if you are only seeing 1 volt at the starter purple wire you should expect to see 11 volts on the voltmeter…that voltmeter reading is the voltage drop across the switch…if you see a minus sign on your voltmeter don’t worry about that…just look at the number…if seeing a minus just means you have to switch the leads around…you may also have high resistance on either the clutch or park/neutral switch.
Melting Slicks
Joined: Sep 2008
Posts: 3,138
Likes: 802
From: Espanola New Mexico
The second test failing means that the BCM is not supplying a negative or ground on the yellow black stripped wire and thus the TDR will not energize and send 12v on the violet wire. Is the Security light off when the key is turned to the On position. The BCM supplies a ground to the TDR if the BCM receives the correct signal level from the Ignition switch contacts that press against the keys resistor pellet.
Heel & Toe
Joined: May 2024
Posts: 15
Likes: 1
The second test failing means that the BCM is not supplying a negative or ground on the yellow black stripped wire and thus the TDR will not energize and send 12v on the violet wire. Is the Security light off when the key is turned to the On position. The BCM supplies a ground to the TDR if the BCM receives the correct signal level from the Ignition switch contacts that press against the keys resistor pellet.
Heel & Toe
Joined: May 2024
Posts: 15
Likes: 1
The second test failing means that the BCM is not supplying a negative or ground on the yellow black stripped wire and thus the TDR will not energize and send 12v on the violet wire. Is the Security light off when the key is turned to the On position. The BCM supplies a ground to the TDR if the BCM receives the correct signal level from the Ignition switch contacts that press against the keys resistor pellet.
Melting Slicks
Joined: Sep 2008
Posts: 3,138
Likes: 802
From: Espanola New Mexico
There is one thing you can try and that is disconnecting and reconnecting the negative battery cable after a few minutes. If the car cranks over it means the BCM is causing the no crank. Do you hear the TDR click on when you turn the key to the start position of the Ignition switch?