Diagnosing starting issue

SnowyOwl

Newbie
Joined
Jan 26, 2025
Messages
14
Location
Finland
Vehicle Details
1994 Ford Thunderbird LX 4.6
Country flag
What I'm getting when I turn the key to "START" position:
- Voltage meter drop, electronics (clock, blower motor) go off
- No crank, no click, no voltage at the starter "S"-terminal/"wake-up"-terminal

What I'm getting when I pull a jumper cable from battery to the S-terminal, and connect the cable when key on RUN position:
- Car starts and runs fine

-> Looks like MLPS.
- However nothing changes with new sensor.
- Tested old sensor with resistance meter, it gives 0 ohm resistance on Neutral or Park position, inf on other positions. (I.e. it seems to work)
- Also ensured that the sensor is installed in the correct position
- Rewired the sensor connector, it had some corrosion, but not much. No help.
- Tested that 5 V is present on the MLPS's cable harness EEC module signal cable, when key is on RUN position.


There ain't too many places left to check. When the MLPS harness is disconnected, is it safe to try starting, and check if I get voltage on the ignition switch cable, or will I burn something in the EEC or so? That would help to rule out if it's the ignition lock not passing voltage through.

Any other places I should check? No OEM anti-theft in this car. There's some aftermarket system installed, which should be disabled. I'm assuming problems on there if the ignition lock appears ok, though.
 
Last edited:

Similar threads

Back
Top