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Toyota Service
Toyota Service, Lexus and Toyota expert
Category: Lexus
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2004 Lexus GX470, last month experienced intermittent

Customer Question

2004 Lexus GX470, for the last month experienced intermittent starting problems. Turn the key, one slight click first try... nothing after. Disconnect battery cable and reconnect, starts every time.
Then while driving the vehicle died, all electrical seemed fine, more like fuel cutoff. Now every attempt to start is the same sequence of events, first try one click. Second car turns over and won't start or if it does runs rough for a few minutes and dies. Third try starter won't disengage until key is turned to off position.
Any help would be much appreciated! I'm a car guy and do most of my own maintenance, but this is beyond my abilities.
Submitted: 1 year ago.
Category: Lexus
Expert:  Toyota Service replied 1 year ago.

Hello. Welcome to Just Answer. Please allow me to assist you. This sounds like 2 different p[roblems at the same time.

The one click is the starter solenoid/relay contacts being drawn together via the key in the start position. The click and no rotation of the starter motor indicates the contacts are worn. They can be replaced, or, if the starter has a lot of miles on it, replace the starter.

The starter running until the key is turned off indicates the start position on the key switch contacts is sticking. The contacts should disengage when the key is released form start. In this case, I would recommend replacement of the electrical half of the ignition switch if your ignition features a removable switch assembly (which would be screwed to the back of the ignition lock assembly).

The cutting off also seems to indicate faulty contacts in the ignition switch. If the contact is broken, the relays drop out (no power) and the engine shuts off.

If this vehicle was in my shop I would be replacing the starter motor and the ignition electrical component on the back of the ignition lock assembly.

Expert:  Toyota Service replied 1 year ago.

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Customer: replied 1 year ago.
That can't be it, because the fail to start was corrected by disconnecting the battery cable and then reconnecting. The dying can't be an ignition problem because the car runs for a minute or two (10 minutes once) but won't idle. If you touch the gas pedal while it is running it dies. This is some type of computer issue, has to be electronic based on the intermittent nature of the problem.
Customer: replied 1 year ago.
The starter won't disengage unless the car starts, it does disengage if it starts. Sorry, I just figured that part out.
Customer: replied 1 year ago.
To clarify, the current issue is that the car won't run more than a few minutes at a rough idle. I gave the background because the random issues seemed to point to the ECM and I wanted to verify that before buying a $700 computer. I think I provided too much info and confused the issue.This morning the car turned over and started, it ran for about two or three minutes at an up and down idle... it would run rough and the rpms would drop, then it would pick up to a normal idle for 30 seconds or so... and then drop again... finally dying. When I tried to start it again, the starter engaged and continued to turn until I turned the key off. (because the car did not start)
Expert:  Toyota Service replied 1 year ago.

Please allow me to ask if the check engine light is on when the engine is running.

Customer: replied 1 year ago.
No, the maintenance required light came on recently, but no check engine light.The intermittent start problem is back. Same deal, disconnect and reconnect the battery and it cranks.
Expert:  Toyota Service replied 1 year ago.

Does the check engine light come on when you turn the key to the on position ( like where the key would be if the engine is running)?

Customer: replied 1 year ago.
the check engine light is on when the key is in the on position. When you first turn the key all of the lights illuminate, but when the key is in the on positions several lights including the check engine light remain on.
Expert:  Toyota Service replied 1 year ago.

Normally, if the Check engine light does not come on with the key on, this indicate an ECU internal problem. I am not sure you need an ECU. If you have no codes, you may have a mechanic al issue, like a leak at the air tube between the mass air sensor and the throttle body.

Customer: replied 1 year ago.
Do you mean the check engine light should not be on wit the car running or with the car not running and the key in the on position?
Customer: replied 1 year ago.
Because the check engine light DOES come on with the key on... which... if I am understanding you correctly would indicate that the ECU is ok?
Expert:  Toyota Service replied 1 year ago.

The light coming on with the key on is the check feature for the check engine bulb. If the computer is bad the computer will not power up the check engine light. The light should ba OFF when the engine is running. This is normal. Only if you have a problem (electrical), the light comes on and stays on. The light being on, when the engine is running, indicates a problem in the engine system. The light can also come on if the computer is bad. If your light is off when the engine is running, I would be inclined to think the ECU is ok.