Rx300 2002 Intermittent Cruise Control Fault

[PaulDD]

Hi all I have a 2002 (old shape) RX300 bought it with 75K on the clock and now has 103K.
It has an intermittent problem with the cruise control thats driving me nuts.

If I set the cruise control to ON the green cruise light shows on the dash and it will work for approximately 40 miles sometime around then the cruise light will flicker off/on and disengage the set speed, the cruise light will remain on. The further you drive the car and more you reset the cruise control the worse the problem gets.

The Cruise light shows 4 different symptoms starting at one and progressing through

1 - flickers off for a fraction of a second disengaging the set speed
2 - flickers off for a fraction of a second refusing to set a speed T
3 - flickers on and off in a series of patterns (as it gets worse)
4 - it goes off completely. The only way to get the light back on is to press the on/off button Twice or turn the ignition off then restart the car and press the on/off button once (eventually)

I generally drive between 50-60 mph but the fault does not seem to be speed related. I have actually had the car stood on the drive engine running cruise control ON (having returned from a trip up the motorway). Pressing the cruise control stick down as if to set the speed resulted
in the Cruise light flickering off for a second exactly as would when driving but refusing to set a speed.

When the fault is showing turning the ignition off and restating the car doesn't clear the fault. Leaving the cruise off or not trying to set a speed for some length of time while driving does seem to bring it back to some form of intermittent operation but not for long.L
leave the vehicle until the next day and its good for another 40 miles or so on cruise.

I had an Independent repairer check the On board diagnostics and they came back with three fault codes

B1421 passenger side Sunlight penetration photo Circuit defective
C1223 Control Unit Faulty Operation
C0278 Relay Solenoid Valve Open/Close Circuit

Has anyone had anything similar and what was the fix please?

Any Ideas Anyone? PLease

[ChrisKaye]

Hi, your first two codes are climate control related with other posts on the forum discussing them.

That last code was tricky to track down as the 'C' series codes all differ between manufacturers, however, I think it is the key to your Cruise Control issue - c0728 is "Right Front Accelerometer Circuit High Input" which I believe ties into the VSC/ABS system, a fault code raised whilst driving would cancel Cruise Control.

Unfortunately there doesn't appear to be much info for troubleshooting the above error, nor any pictures of parts etc to help!

It is possible some wiring may be worn or have a poor ground or connection and cleaning/reseating plugs could help.

Does anyone have access to a service manual that could chip in with more info?

[PCM]

Does this help?

http://my.is/forums/f87/did-shop-mess-up-my-abs-536593/

[ChrisKaye]

Hi pcm, the code in that article was c0278 and the original poster mentioned code c0728 (although could easily be a typo!)

If the problem was the ABS wheel sensor, at least that would be easier to check as you would know where to start looking for it (the wheel!) - when I had the struts off my RX recently, there's no accelerometer on the strut or hub, so I have no idea where this sensor is located... :/

[PaulDD]

Hi Everyone thanks for the reply's, unfortunately this has had to move onto the back burner for me just now as another problem has arisen. ​
Long story Short:. On the way up to Scotland before Christmas the RX developed what sounded like a bearing noise.
I suspected the water pump. Took it into a Lexus dealer on a Saturday morning one of their guys had a listen and agreed it could be a water pump but would need to see under the casing to be sure. They had the car Monday fitted a water pump and on the journey home the noise re-appeared. It took my local dealer in Sheffield under 2 mins to diagnose the actual problem as an air-con pump. So now I'm £480 out for a water pump fitted that wasn't needed and will be another £500+ out for the air-con sorting.
Currently not a happy bunny :megaangry:

Before making the journey up to Scotland An auto electrician had a look at the RX cruise control issue. His analysis was possibly a solenoid in the ABS pump but it could also be the Cruise ECU he is leaning to wards the ABS solenoid because of the "C0278 Relay Solenoid Valve Open/Close Circuit" he is getting from the on board diagnostics. That said because he wasn't able to look at the vehicle while the problem was actually apparent understandably he couldn't say what it was for certain - Aint intermittent faults wonderful?

Feel free to chip in with suggestions still if wish. If/When I get it sorted I will post on here to try and help others in the same predecament....

[ChrisKaye]

That's ridiculous, I don't even know where to start on how bad the service you received was. I bet they didn't even change your cam and drive belts either... Assholes.

The least they could do is charge you cost price for the water pump (<£90), and fit an air con compressor (which you source and supply) free of charge...

[PaulDD]

Have to say I would never touch Lexus Scotland again not even with a barge-pole and full decontamination suit after my experience. Only after getting Lexus UK involved the best they would do is refund cost of parts, which works out at LESS THAN 50% of the bill highly un-impressed - Avoid like the plague....

The car has now cost me £700 for the AC unit fitted at a non Lexus but good quality garage the problem now is I have the b***dy Battery apparently discharging and the Alarm randomly triggering.....

Needless to say still no solve on the cruise control 

[PaulDD]

Have to say I would never touch Lexus Scotland again not even with a barge-pole and full decontamination suit after my experience. Only after getting Lexus UK involved the best they would do is refund cost of parts, which works out at LESS THAN 50% of the bill highly un-impressed - Avoid like the plague....

The car has now cost me £700 for the AC unit fitted at a non Lexus but good quality garage the problem now is I have the b***dy Battery apparently discharging and the Alarm randomly triggering.....