Mystery Diagnosis ??

[arbetrader]

WHY WON'T MY LX START?

I honestly have no clue what's going on here...

Once in a while (happened 3 times now) when I go to start my truck, it just cranks and cranks but does not fire. I cannot figure out what is happening, although I have an idea or two...

Here's where this started:

Last summer at our cottage I parked my truck as usual, locked/armed the vehicle with the factory lexus keyfob. 1.5 hrs later when I went to start it, it just cranked but did not fire. I was able to walk back to our cottage and grab my other set of keys to try and I got a ride back to the truck. Tried immediately again - no luck. I then opened the hood, looked at all the plugs/wires etc, disconnected/reconnected battery and tried some various troubleshooting ideas however none of them worked. Then I played around with the locks locking and unlocking quite a number of times, and opening/closing the door in a similar fashion to someone trying to code a new key. After about 2 mins of doing this I tried again, and voila! It worked. My truck has started/ran fine (wonderful at that) for the last 3 months without issue.

Last week:

I was leaving work, and once again, the same thing happened. This time I only left the truck for no more than 5-10 mins (locked/armed as always) and when I returned, again just cranking, and no firing. I tried cranking for quite a while (being sure not to overheat starter of course) on and off, but to no avail. I tried doing the doorlock/opening/closing dance again - but this time that didn't work. I then hit the alarm button on my keyfob, then immediately disarmed it by hitting the unlock button, then went to start the vehicle, and voila! It started. Since then, we've used it regularly without problem for at least 15-20 starts I'd think. No issues.

Today:

I was at home, Vehicle was locked/armed as usual, and had been so for about 1 hr or so. I unlocked as usual, went to start, and exactly the same issue was happening again. This time I tried the door/unlock/brake pedal dance again, no worky. I tried doing the alarm/disarm thing numerous times, that also didn't work as it did the last time. I tried the other set of keys, no help. I tried the alarm over and over, no worky. Then, I tried hitting the alarm button one more time, but this time I tried to start the truck with the alarm going off - Voila! It started. What's going on with my rig? My LX otherwise runs like a dream, and the thought of replacing it with something less worthy is hard to picture, although reliability is very important to me as this is my wifey's & 3 kids main vehicle.

Facts:

- No unusual sounds or smells during any of this
- Vehicle: 1999 LX in my sig - 197k Miles
- I'm not sure if the fuel pump has ever been done - I doubt this is a fuel issue due to the way this is happening, and the truck runs super smooth otherwise.
I really think this is ignition related or something to do with the way the truck sees the sensors in each keyfob. 1 keyfob is original, one is a replacement but BOTH are masters, not spares

Secondary fact:

- My wife has always used a master key (with clickers) built into the body of the key.
- For the last 1 yr (until last week) I have been using a secondary key that was cut to fit the ignition chamber however I always had a master bank key that was coded to my ignition right next to the key I used for startup. I'm not sure if that would make any difference. The guy locally here wouldn't' cut it for me so I had it cut at a locksmith while I was in the city last week. As you can imagine, I don't head out there much, and even so, it was not a big priority of mine, but after last week's occurrence, I had this done nonetheless.

Sorry about the long thread but I figured the more info the better.... Thanks for any advice or ideas anyone can provide

 

[AimCOtaco]

You need to observe the behavior of the security light when this is happening. That will tell you if it is the imobilizer or a more conventional failure. Also note the fuel tank level when it happens.

 

[arbetrader]

You need to observe the behavior of the security light when this is happening. That will tell you if it is the imobilizer or a more conventional failure. Also note the fuel tank level when it happens.

You know, that same thought crossed my mind, I was looking at the security light and noticed it was flashing during this time, but I'm still not quite sure of what I'm supposed to be watching for? How is it supposed to flash normally while unarmed? While driving? While armed? While cranking the engine?

Anyone know?

I think knowing this will help me figure out what's going on the next time this happens. Thanks for the response!

 

[Dobie]

I have an 04' LC. When I unlock my door the light blinks at a slow rate maybe every 3 seconds. Once I place the key in the ignition the blinking stops. I turn the key and start the truck and there is no further blinking as well.

Hope that helps

 

[Travis351]

If its just got the factory alarm and the security light is flashing when this happens, try replacing the EFI fuse under the hood.

 

[arbetrader]

If its just got the factory alarm and the security light is flashing when this happens, try replacing the EFI fuse under the hood.

The EFI fuse? I'm curious as to what this would have to do with the issue... I'm certainly game to try anything though, especially if it's cheap enough I'll try to do this, however I think I'm going to wait until this happens again. In the meantime I'll get the fuse so I'm ready to go.

Btw, the security light DOES in fact flash when this is happening. I expressly remember this happening.

 

[Travis351]

There is a 20 amp spare under the cover ready to go. Swap it out next time she won't start.

 

[AimCOtaco]

Yep, there is some wierd action where the fuse develops a tiny bit of resistance and therefore voltage drop that adds up to a no-start.

The security light should go dark when an 'authorized' key is recognized in the ignition vicinity.

 

[arbetrader]

Ok, I confirmed that yes, the security light is operating as it is supposed to normally; and stops flashing (goes out completely) as soon as I input the key into the ignition. However, when this particular phenomenon is happening I do remember it flashing throughout the entire process of my trying to get the truck to start. Also, although I cannot confirm until the same thing happens again, I'm pretty sure the security light was flashing faster than normal during the this time. Any thoughts on that?

In the meantime, if this happens again, I will try what has been recommended.