1999 Ford Taurus LX No power, No start
Senior Member
Joined: Feb 2024
Posts: 1,273
From: California
No light on dash, do you mean just instrument cluster or no light as well to your climate control and radio?
Key out, when you turn on just the parking light, not headlight yet, go outside the car, do you see any light at all?
Your OBD port ok now?
After reading this entire thread all over again, and you got 12.38V on C121 at terminal 86 (TN/RD wire) that only indicated that your ignition switch and range sensor are doing their job, if your PATS doesn't send ground signal to C121 (at rest), the starter relay still can't energize. Then your car was running fine afterward I assumed the issue has been resolved. Since it hasn't, testing terminal 86 at c121 was just 1 of 4 steps, you still need to test other terminals at C121 (85, 30 and 87).
Therefore check the following:
1) The PATS, check the PK wire at C121 terminal 85, you should get ground signal at all time (unless PATS system is triggered)
Test PK wire with key out and key in RUN position, do you get ground signal on both?
2) Test terminal 30 at C121 (LG/VT wire) you should get 12v at all time do you?
3) Test WH/PK wire at the starter motor (not at C121), run a jumper wire from there to the red lead of your voltmeter, and the black lead to chassis ground, crank it do you get any reading, say battery at 12.45V, like 10V to 12.45V at your voltmeter?
4) Do the same (3) above but this time you test it at C121's WH/PK wire, terminal 87.
Key out, when you turn on just the parking light, not headlight yet, go outside the car, do you see any light at all?
Your OBD port ok now?
After reading this entire thread all over again, and you got 12.38V on C121 at terminal 86 (TN/RD wire) that only indicated that your ignition switch and range sensor are doing their job, if your PATS doesn't send ground signal to C121 (at rest), the starter relay still can't energize. Then your car was running fine afterward I assumed the issue has been resolved. Since it hasn't, testing terminal 86 at c121 was just 1 of 4 steps, you still need to test other terminals at C121 (85, 30 and 87).
Therefore check the following:
1) The PATS, check the PK wire at C121 terminal 85, you should get ground signal at all time (unless PATS system is triggered)
Test PK wire with key out and key in RUN position, do you get ground signal on both?
2) Test terminal 30 at C121 (LG/VT wire) you should get 12v at all time do you?
3) Test WH/PK wire at the starter motor (not at C121), run a jumper wire from there to the red lead of your voltmeter, and the black lead to chassis ground, crank it do you get any reading, say battery at 12.45V, like 10V to 12.45V at your voltmeter?
4) Do the same (3) above but this time you test it at C121's WH/PK wire, terminal 87.
Last edited by heiko; Oct 17, 2024 at 02:06 PM.
Thread Starter
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Member
Joined: Aug 2024
Posts: 48
No light on dash, do you mean just instrument cluster or no light as well to your climate control and radio?
Key out, when you turn on just the parking light, not headlight yet, go outside the car, do you see any light at all?
Your OBD port ok now?
After reading this entire thread all over again, and you got 12.38V on C121 at terminal 86 (TN/RD wire) that only indicated that your ignition switch and range sensor are doing their job, if your PATS doesn't send ground signal to C121 (at rest), the starter relay still can't energize. Then your car was running fine afterward I assumed the issue has been resolved. Since it hasn't, testing terminal 86 at c121 was just 1 of 4 steps, you still need to test other terminals at C121 (85, 30 and 87).
Therefore check the following:
1) The PATS, check the PK wire at C121 terminal 85, you should get ground signal at all time (unless PATS system is triggered)
Test PK wire with key out and key in RUN position, do you get ground signal on both? Yes on both
2) Test terminal 30 at C121 (LG/VT wire) you should get 12v at all time do you? Yes 12.56V
3) Test WH/PK wire at the starter motor (not at C121), run a jumper wire from there to the red lead of your voltmeter, and the black lead to chassis ground, crank it do you get any reading, say battery at 12.45V, like 10V to 12.45V at your voltmeter? Getting 0 volts
4) Do the same (3) above but this time you test it at C121's WH/PK wire, terminal 87.
Key out, when you turn on just the parking light, not headlight yet, go outside the car, do you see any light at all?
Your OBD port ok now?
After reading this entire thread all over again, and you got 12.38V on C121 at terminal 86 (TN/RD wire) that only indicated that your ignition switch and range sensor are doing their job, if your PATS doesn't send ground signal to C121 (at rest), the starter relay still can't energize. Then your car was running fine afterward I assumed the issue has been resolved. Since it hasn't, testing terminal 86 at c121 was just 1 of 4 steps, you still need to test other terminals at C121 (85, 30 and 87).
Therefore check the following:
1) The PATS, check the PK wire at C121 terminal 85, you should get ground signal at all time (unless PATS system is triggered)
Test PK wire with key out and key in RUN position, do you get ground signal on both? Yes on both
2) Test terminal 30 at C121 (LG/VT wire) you should get 12v at all time do you? Yes 12.56V
3) Test WH/PK wire at the starter motor (not at C121), run a jumper wire from there to the red lead of your voltmeter, and the black lead to chassis ground, crank it do you get any reading, say battery at 12.45V, like 10V to 12.45V at your voltmeter? Getting 0 volts
4) Do the same (3) above but this time you test it at C121's WH/PK wire, terminal 87.
Senior Member
Joined: Feb 2024
Posts: 1,273
From: California
3) You got 0 volt means 2 possibilities:
a) Your relay is not energizing at all
b) Your WH/PK wire has bad terminal(s) or connection on either or both ends
All depends on what you get at (4) so what you get at (4)?
If you get 0 volt at (4) as well before you replace the relay, remove the relay, jump terminal 30 (LG/VT wire) with the WH/PK wire directly with a thick cable without using the key in ignition to crank, do this with caution, your starter should crank.
If your starter cranks, buy a new relay. If it still doesn't crank, check the WH/PK terminals and wire, if it's good for sure, then your starter could be bad as well and you need to jump LG/VT wire directly to the WH/PK trigger wire directly.
A no crank no start is all about electrical and its connection: battery -> fuse (to protect ignition switch) -> ignition switch -> range sensor -> fuse (to protect the starter relay even it's labeled range sensor) -> starter relay -> starter motor
So technically to crank (whether or not it's able to start the car), your motor and alternator can be off the car, just like when you do a bench test on the starter, those are not required.
a) Your relay is not energizing at all
b) Your WH/PK wire has bad terminal(s) or connection on either or both ends
All depends on what you get at (4) so what you get at (4)?
If you get 0 volt at (4) as well before you replace the relay, remove the relay, jump terminal 30 (LG/VT wire) with the WH/PK wire directly with a thick cable without using the key in ignition to crank, do this with caution, your starter should crank.
If your starter cranks, buy a new relay. If it still doesn't crank, check the WH/PK terminals and wire, if it's good for sure, then your starter could be bad as well and you need to jump LG/VT wire directly to the WH/PK trigger wire directly.
A no crank no start is all about electrical and its connection: battery -> fuse (to protect ignition switch) -> ignition switch -> range sensor -> fuse (to protect the starter relay even it's labeled range sensor) -> starter relay -> starter motor
So technically to crank (whether or not it's able to start the car), your motor and alternator can be off the car, just like when you do a bench test on the starter, those are not required.
Senior Member
Joined: Jun 2010
Posts: 16,662
It has been just about a month and still can't get the vehicle to start.
You corrected the battery problem, but did you make sure the positive feeds to the inside of the vehicle were all clean and tight and grounds too ?
Did you try your second key ? The passive anti-theft system in your vehicle will prevent the starter from operating if the key lost it's coding ?
You corrected the battery problem, but did you make sure the positive feeds to the inside of the vehicle were all clean and tight and grounds too ?
Did you try your second key ? The passive anti-theft system in your vehicle will prevent the starter from operating if the key lost it's coding ?