99 Rx 300 I've changed 6 sensors in the last 10 months. 2 air fuel ratio(on bank 1 and 2), 2 knock sensors, top dead sensor, and the sensor in the air inlet on the air intake, next to the filter. Next thing was the engine quit running, bad fuel pump in the gas tank. After the fuel pump change, engine wouldn't start.
When you put a tester on the injector nozzle it showed no voltage, when turning the engine over. Now here is the interesting part: When a Snap On analyzer pad was connected to the plug, inside the car, the car would start and run just fine. As soon as you unplugged the analyzer the engine would quit. It did throw off a bad camshaft sensor, but that was intermittent. Also the engine threw off no codes, indicating nothing was wrong. This piece of garbage is cleaning out my bank account. My mechanic is dumb founded. Lexus never heard of this. I am hoping someone out there has had this problem. Thanks in advance for all that you do, I appreciate the help.

 

Sorry to hear that your RX is giving you trouble.

What was the last thing that was done to the RX after which it quit running?

There are number of ground wires behind the intake (near fire wall). Please see DIY on knock sensors.

I would trace in this order
Spark
Fuel
Air
Timing

Salim

 

I think you have a main or ECU fuse blown. When you connect the analyzer, the car will actually get ECU power from the analyzer and run. Disconnect and it dies. Explains the fuel issue too, no ECU power, no fuel pump power. That's where I would start. Not sure where the fuses are, but that's my bet.

 

Awesome!

If this solves OP's problem, he owes you a whole lot.

2 merit stars from me.

Salim

 

We will see if that's right. I never actually encountered this, but have heard of it. There is another version of this that is supposed to be a bad ground and the scanner completes the circuit. Either way, if it only runs with a scanner, the ecu is not getting power. Check fuses and grounds. I think you can short two pins on the OBDII connector (not sure which ones) and find out if it is the ground issue.

 

To test the theory, i would check pin 16 on the obd2 connector to see if a 12v+ signal exists. If so, then the ecu is getting power from the battery.

The OP mentioned issues started with the fuel pump change. I would check all connections related to that work and the fuel pump relay.

 

This happenned to me- was a bad ground....the one behind the upper intake manifold. My ECU ground was showing 7 volts on it!