LX shuts off and will not crank to restart

[verylatenight]

Challenge - LX shuts off and no restart
Performed the 90K service, timing belt, water pump, valve lash, spark plugs, other checks. I've changed plenty of TB and a few on a LC as well. The LX470, 2006, fired right up and settled into a smooth idle. It did present the VGRS light but I suspect that was from some fluid leaking from the removed hose. Shut it off to top the antifreeze and then it would not crank to start. Checked all connections. Reset codes by disconnecting battery. No crank. Left it for a few hours and then it fired right up. Next day I drove it around the block to reset the steering light, which it did, then drove it about a mile and it died at the stop light. No cough or sputter, just died. It restarted and drove a few miles, and it died, luckily I coasted to a parking lot. It then would not crank. A few hours later it fired right up. Repeatedly shut off and restarted. Drove it home and at one point it felt like all power cut off for a half second and a mile later it died again. The check engine light never went on. Disconnecting the battery to reset the ECU did nothing. I want to note that I did spray cleaner on and in the throttle bottle butterfly and cleaned it with a rag. Also used electrical cleaner on the sprockets before installing the TB to remove antifreeze but later learned it is not recommended. Did not use a code reader yet because the CEL is not lit.

I offer this challenge to come up with a viable solution. I have a vast technical background but this is a new one.

 

[Bawlz]

Shoot, I wrote a reply about it possibly being the cam sensor, then I re-read your post, and you say no crank, not just no start. So it's no crank sometimes, and it dies with no-start sometimes?

Here's a thread about several '06s dying when heat soaked:

https://forum.ih8mud.com/100-series...ting-off-during-long-trips-4.html#post8698483

Here's the TSB, apparently it can happen without setting then Check Engine light.

https://forum.ih8mud.com/attachment.php?attachmentid=787354&d=1375371848

Obviously your engine isn't heavily heat soaked, but if the sensor is prone to issues, it may be worth looking into.

Also sounds like the starter might be bad?

 

[verylatenight]

If it was only no crank then I would look at the starter. But it sheets down abruptly, then no crank. This is not logical for either the starter or the cam sensor. Is the oil pressure sending unit tied to a no crank scenario?

 

[Bawlz]

Very true. It actually sounds a bit like a bad ground, as if a large ground cable connection is loose at the block. The connection is lost just enough, it dies and won't restart, then the connection is restored just enough, and you are able to start it. Just a thought anyway.

The oil pressure is not tied to a no crank scenario (or no start for that matter).

 

[verylatenight]

Will check out the grounding. The charging wire was removed for the timing belt change, but no grounds.

A bad crank position sensor would explain the abrupt engine stop, but that does not explain why it would not crank to restart, unless it sets a code without setting the check engine light and this code is not reset when disconnecting the battery for a few minutes. I am tempted to tear the whole front off again but fear I will not find anything.

 

[Throttle Crazy]

I agree that the first step is to check for a loose ground connection or even positive connections. I would even voltage drop test the grounds. If this problem did not occur prior to the work you did check the harness around the area u worked. Another obvious component to cause this issue would be an ignition switch failure. I would make sure that there are no connectors u unplugged that may have backed out a pin causing bad connection or got coolant in them when u were Disconnecting hoses or water pump. If u have access to a wire schematic I would look at the starter circuit and start there. Should be pretty simple to diagnose if its a no crank. Ignition switch, relay, cables and starter. Start at the starter relay and see of u are getting signal to crank, u have good power and grounds at relay. If there is no signal to energize the relay then u have to look back toward computer and ignition switch possibly security system also. If u have everything good at the relay it has to be between the relay and the starter.

 

[verylatenight]

The left bank spark plugs ae under a rather large wire bundle, and part of this appears to go back to the starter area. I will deep dive into this first. Nothing was touched in the ignition switch area and when it does start, I can start it 5 or more times in a row without fail. Seems when it runs about 10 minutes it begins to have issues.

 

[Throttle Crazy]

My point on the ignition switch is it could cause the issue and would be just a coincidence that it happened after working on it. More likely going to be a loose wire connection that builds resistance as it heats up and breaks connection. The starter relay in the under hood fuse box is just an easy access point to see what's going on with the no crank. U can voltage drop a ground, power and check the energizing signal in about 10 min. If it is all good has to be problem in harness between starter and relay. Starter signal won't cause it to die while running but if there is a fusible link that runs in the same harness to the starter could cause it to die. Would have to see schematic. I will look to see if I can find the schematic if I get time.

 

[verylatenight]

Finally had the LX brought to the dealer and after 2 hours they state that one of the wires to the camshaft postion sensor is damaged. Seems that if the power supply wire to the CPS is damaged the ECU will shut all engine functions down (but not generate a CEL?), but damage to the another wire will generate a misfire and CEL and codes.

Will tear it apart and post an update when solution is confirmed

 

[verylatenight]

Confirmed. The power wire on the cam sensor was between the head and the rear plastic guard. Got under there when putting the outer guard on and slipped between them, pinched a hole and would shut off the ECU, so no crank or engine kill without generating a code.