Confusing Error Code and Diagnosis by Lexus

[Blessing]

Hello everyone. 

I have the Check Hybrid System and the Check PCS fault in my RX 450h. I took it to Lexus for a proper diagnosis and they said there were two codes :

PAOO6 526. 

PAOO6 611

I was thinking it will point to something in the hybrid system but to my shock, they said I need to replace the air conditioning compressor. 

Do you think the diagnosis is right? 

Is the job too complicated for my local garage to handle? 

 

 

[Herbie]

More than likely correct, yes.

The aircon compressor is driven by a 500V 3-phase AC variable frequency motor and the motor windings are submerged in the lubrication oil for cooling purposes.

In conventional cars the oil is known as PAG oil but to put it simply, that oil will conduct electricity. Hybrids need to use ND11 oil which is a high dielectric oil and does not conduct electricity. It's been found that as little as one percent contamination of ND11 by normal PAG oil will cause electrical breakdown of the motor windings.

It appears that at sometime in its life, the aircon has been serviced and regased using the wrong oil. The refrigerant gas itself is the same, just the oil that must be different. Those error codes are showing that there's a breakdown of the electrical insulation in the compressor motor and the system is trying to prevent high voltage leakage to the car metalwork so that you don't get electrocuted.

[Blessing]

26 minutes ago, Herbie said:

More than likely correct, yes.

The aircon compressor is driven by a 500V 3-phase AC variable frequency motor and the motor windings are submerged in the lubrication oil for cooling purposes.

In conventional cars the oil is known as PAG oil but to put it simply, that oil will conduct electricity. Hybrids need to use ND11 oil which is a high dielectric oil and does not conduct electricity. It's been found that as little as one percent contamination of ND11 by normal PAG oil will cause electrical breakdown of the motor windings.

It appears that at sometime in its life, the aircon has been serviced and regased using the wrong oil. The refrigerant gas itself is the same, just the oil that must be different. Those error codes are showing that there's a breakdown of the electrical insulation in the compressor motor and the system is trying to prevent high voltage leakage to the car metalwork so that you don't get electrocuted.

Thank you so much Herbie. 

You have made things a lot clearer for me. Do you think my local garage can change the compressor? 

Lexus is charging me 3k to do the job. 

Does the compressor really need to be changed or can the oil only just be changed? 

[Herbie]

First of all Blessing, check those error codes - I think you'll find that they should be:

P0AA6 rather than PA006

If I'm right then the screenshot below will help you understand the problem:

526 shows possible areas in order of possibility but 611 narrows it right down:

And to give you an idea of what's possibly happened, the photos below show the windings of a motor that has gone (a) short-circuited coil and (b) shorted turn. The copper wires have got enamelled insulation and you can see where the insulation has been damaged, which is likely what's happened to your compressor motor.

I'm afraid that yes, the whole compressor will have to be changed because it's all one unit - a combined compressor, motor and inverter. Just a guess but I'll be that the part alone costs over a grand.

And the whole aircon system will need to be thoroughly flushed to make sure that not a single drop of PAG oil remains to contaminate the new compressor assembly.

[Blessing]

Thanks Herbie. It all makes sense now. 

[Blessing]

I belive I owe this forum an update and a big thank you, especially to Herbie. 

I only just had an RX 450h SEL 2009 for a few weeks when the problem started. The symptoms is the Check Hybrid System orange triangle usually shows up. Few minutes after I turn on the heater or the air conditioning, the Check PCS warning light comes on as well. The air conditioning was just cool, never cold.  Every few days the car will refuse to start until I get a mechanic to clear the warning lights. The Check PCS light do go off when the car is turned off and switch on again. 

I took it to Lexus for a proper diagnosis and they said I need to change the air conditioning compressor. That it seems when the car was regassed the wrong oil was used. They quoted my £3k for parts and labour. 

I got a used compressor from eBay for £185 and my mechanic fixed it including regasing for £300. Now the air conditioning is ice cold. No more check hybrid warning light. No more check pcs warning light. Thank God. 

Interestingly when I took it to lexus, the engineer was almost swearing that my car has no PCS. I explained to him the the check pcs warning light do come on and even showed him a small PCS BUTTON hidden above the accelerator pedal. But he insist a 2009 third generation RX does not have it. 

[Herbie]

46 minutes ago, Blessing said:

I belive I owe this forum an update and a big thank you, especially to Herbie. 

You're very welcome my friend, glad to hear that it all worked out alright for you in the end and thanks for keeping us informed.

Hopefully you can now just enjoy the car as you waft along in comfort and keep your cool

[ColinBarber]

9 hours ago, Blessing said:

Interestingly when I took it to lexus, the engineer was almost swearing that my car has no PCS. I explained to him the the check pcs warning light do come on and even showed him a small PCS BUTTON hidden above the accelerator pedal. But he insist a 2009 third generation RX does not have it. 

It sounds like you have an SE-L Premier rather than just an SE-L. PCS was standard fitment for the Premier in 2009.

https://www.lexusownersclub.co.uk/forum/topic/94267-rx-450h-series-3-equipment-specifications-2009-2015/

 

[Blessing]

14 hours ago, Herbie said:

You're very welcome my friend, glad to hear that it all worked out alright for you in the end and thanks for keeping us informed.

Hopefully you can now just enjoy the car as you waft along in comfort and keep your cool

Yes it's now a pleasure to drive. 😁

[Blessing]

5 hours ago, ColinBarber said:

It sounds like you have an SE-L Premier rather than just an SE-L. PCS was standard fitment for the Premier in 2009.

https://www.lexusownersclub.co.uk/forum/topic/94267-rx-450h-series-3-equipment-specifications-2009-2015/

 

All the official records and documents states it is SE-L. But it has PCS, Wood Trim and HUD. The shocks are spring. 

[ColinBarber]

3 hours ago, Blessing said:

All the official records and documents states it is SE-L. But it has PCS, Wood Trim and HUD. The shocks are spring. 

It's an SE-L Premier then, unless it is some early pre-launch demonstrator before the UK spec was officially locked down. I've certainly seen other models in the past with a spec that doesn't fully match the 'official' spec.

Both the SE-L and Premier had air suspension. Maybe yours has been converted to standard springs, or again an early model before specs were properly set.