More LS Excitement


LVC Member
Jul 23, 2018
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Hunstville, AL
2004 LS V8, 168K miles. Got in this morning, turned the key and nothing. Warning lights go out as usual with the key in start, but no crank and not so much as a click from a solenoid. Check the battery, up to full charge, terminals clean and tight. Tried starting again, same result (sign of insanity, I know) Turned on the headlights and tried to start, no crank and the lights did not dim. Apparently the signal to crank is not getting to the starter solenoid. Anyone have a wiring diagram showing the starter circuit? I expect I need to start looking for the lost voltage between the starter and the key switch.

Oh, almost forgot...this afternoon I decided to try again in the hope it might start so I could get it out of the driveway so we could at least use the other vehicles. It cranked right up and I shut it off and tried several times again and it started each time. So now if you go somewhere you never know if you're going to get home..."do ya wanna gamble, well do ya?"
Might also want to check a fuel pump driver module, and fuel pump and circuit. That also could be an additional thing to trouble shoot before paying for other parts.

Hope this helps.... Others will also be chiming in shortly.
Not sure if it is possible to turn off the LS without the car in Park, but make sure it is fully in Park. Move the shifter more aggressively into Park next time it won't start and see if that was it.
Yes, it's possible to turn the key off in any gear position. Starter will only engage in the park and neutral positions. Might try neutral next time...
No, fuel pump or REM wouldn't prevent the starter from engaging.

Next time this happens, please look at the PATS light and see what it is doing. If it is flashing rapidly, then wait (leave the key in the on position) until it slows down. It will then flash out a two digit code a few times. Report back with that code. (The PATS light is the little red light at the center of the dash at the base of the windshield.)
Fought with this issue a while myself. Swap the starter motor relay with a known good and see what happens.
Follow Joegr first and report back what the PATS light is doing. Your symptoms point directly to that.
Do you have multiple keys? My friend's Taurus did this and it was a bad key that had been working! Changed to her spare key and it fired right up.
Well, the LS decided to leave me stranded at work, on the coldest night yet. Granted it was only 49, but it was 75 when I left for work this morning.
Anyway, turn the key and I hear the fuel pump (I think) and that's it. The dash lights come on with the key in "run" and go out when I turn it to start. Now the PATS light - when I turn the key to start it comes on steady. If I turn the key to start and hold it even though there is no life in the start circuit (my assumption) the PATS light goes out. Holding the key in the start position for a full minute, dash lights are out, PATS light is out. The headlights come on because it is dark and they don't dim when I turn the key to start. No blinking from the PATS light.

I hope there is a clue in there somewhere. In the old days I'd be looking for a relay not energizing the starter solenoid. What do you guys think.
Well, the LS came home on the hook Friday morning. I tried starting it with both my key and the wife's key and no joy. Same reaction. When it failed to start Thursday night I pulled the starter relay #15 in the underhood fuse box and re-inserted it but no luck. So this morning I tried to start it again and got the same result. I then swapped the #14 and #15 (the part number molded on top is the same for both) relays and it started right up!? So am I looking at just dirty contacts or have I just put a problematic relay in the PCM circuit?

This morning I'm going to pull each relay and clean all contacts. I'm also going to swap the relays back and see if I can re-create the problem. I guess I'm just confused.
I would replace the relay. BTW, your description indicated that PATS was working correctly, and that the PCM was getting power. For the most part, that leaves the starter relay, the starter, one big fuse, and a little bit of cabling. I would have suggested swapping the starter relay out first. I know, you're asking where was I. I was home with no power and no internet after being hit by Zeta. We just got both back.
Hey, thanks for your reply Joe. Sorry to hear that Zeta hit you, hope there wasn't too much damage to your home and area. You folks have had more than your share of serious weather this season!

I swapped the relays back into their original position and the car still starts just fine. These relays run about $16 so I'm going to replace it anyway. I thought that a bad or dirty contact might have been the original problem which is why I tried removing it and re-inserting it in the parking lot.
Replaced the starter relay and it worked for a couple of days. Then, same symptoms and stranded in a Walmart parking lot. Swapped relays with no joy. Called the wife and then tried again and it started! Called her back and drove home.

I pulled the relay and looked at the five slots in the socket. Got out the trusty VOM and started poking. The slot at 12 o'clock, no voltage present. Slot at 3 o'clock appears to be a ground, at least is showed continuity when I tested between it and a ground on the block. Slot at 6 o'clock had 12V. Slot at 9 o'clock no voltage present . The fifth slot, in the center, no voltage or ground.

I'm guessing that if I jump the 12 o'clock and 6 o'clock slots I'll probably energize the starter...but will I damage something like the PCM or some other electronics in the car?
You should be fine, this is how a compression check is done. FWIW, this is also how you can permanently bypass PATS. Once an engine is running, PATS has no influence. If you can get the right terminals jumped, with your key on, the engine will fire up.
It sound like you do have a bad connection either at the relay/fuse box, the starter or a break in the wire between.
If you have the parts available you could do a pin-drag-test (Test the for sufficient clamping force on the connection on each pin at the socket).
Inspect the electrical connections at the starter and...
test resistance of the power wire between the relay socket and the starter solenoid (try wiggling the fuse box while checking for continuity).

Your problem may be in the starter but this way you rule everything else out.
This evening after work the old car didn't want to crank again. I pulled the relay and took a jumper wire I had for this occasion, having used it previously with success (thanks milehighmikey). But this time, nothing. No spark when I made the jump connection. I suspect my problem is in the wiring harness. Feels like pulling the relay might be pulling the terminal away from the wire it is supposed to be crimped to. Shoved the relay back in and the car started. This week I'll take the time to inspect the relay connections in the fuse box but I haven't a clue how to reconnect the wire to the terminal if that's the problem. Looks like a real rats next of wire enters the box but I can't see how you would access a detail wire or two.

Of the five terminals on the relay four make sense to me but the center one I have no clue what it is supposed to do. Until I figure out what to do for a permanent fix I may try to locate a 12V source and connect it to the starter with a push button. With cold weather arriving I need this car to get to Harley isn't adept at negotiating ice.
...This week I'll take the time to inspect the relay connections in the fuse box but I haven't a clue how to reconnect the wire to the terminal if that's the problem. ...

Soldering is the most practical reliable way.

...Of the five terminals on the relay four make sense to me but the center one I have no clue what it is supposed to do. ...

In this case, the center one (87a) does not do anything. There is no connection to it.


Terminal 86 is fed 12V when the key is in the start position and the transmission is in park or neutral via fuse 1 in the cabin fuse box (the fuse is only live when the key is in the start position). Terminal 85 is connected/switched to ground via the instrument cluster. The instrument cluster will only do this if the transponder in the key correctly interacts with the PATS.
Terminal 30 is fed 12V at all times via fuse 21 (30A) under the hood.
Terminal 87 goes to the solenoid on the starter.

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