Error code C1378

[JRSM]

Lexus have diagnosed error code C1378, as the ABS and P/S lights are on, plus a red warning triangle and check AWD, hybrid and VSC. I have been told they need to replace the ABS block relay and the anti skid control module. They have not checked the wheel sensors nor reset the ABS control module. 

Any advice really appreciated.

[Herbie]

13 minutes ago, JRSM said:

Lexus have diagnosed error code C1378, as the ABS and P/S lights are on, plus a red warning triangle and check AWD, hybrid and VSC. I have been told they need to replace the ABS block relay and the anti skid control module. They have not checked the wheel sensors nor reset the ABS control module. 

Any advice really appreciated.

With that many lights up the first thing I'd do would be to have the 12V Battery tested. When they start to go they can produce all kinds of weird and wonderful light displays.

[ColinBarber]

C1378 is related to the brake control redundant power supply, and its communication to the skid control module, so has nothing to do with the wheel sensors. What they are saying is correct, assuming they have ruled out a wiring issue which Lexus list as the first thing to check (and therefore most likely thing to cause the fault).

[steve2006]

The very top line of  the diagnostic page also mentions that the system is activated “when the auxiliary Battery (12 V) voltage drops”

Given the location of both modules ( engine bay and boot) I doubt the wiring loom has been checked.

The power supply cost is bad enough, the skid control computer cost virtually writes the car off!

[JRSM]

On 6/3/2021 at 6:11 PM, steve2006 said:

Hi James and welcome to the LOC.

The first thing to do on any modern vehicle with warning lights on is to have any stored codes read, Lexus being part of Toyota use Techstream to interrogate and diagnose the fault codes. Any decent garage should be able to get the codes read which should point you towards the causes.

Were these lights on before the rear brake job or after?

I’ll also move your post to the RX forum as you may get more responses from there.

 

[JRSM]

Hi Steve,

Thank you very much for your detailed advice. The warning lights were on before the brakes were repaired. The VSC light is not lit, I made a mistake.

The auxiliary 12v Battery, is that the main car Battery?

Thanks, James

I asked Lexus for a written diagnosis , but was told not possible as sent to laptop when plugged in. Previous garage that did the brakes provided attached codes.

[Herbie]

12 minutes ago, JRSM said:

The auxiliary 12v battery, is that the main car battery?

No, that's the 'aux' Battery that starts the hybrid system and runs the 12V systems. In a hybrid the 'main' Battery is the high voltage traction Battery.

13 minutes ago, JRSM said:

I asked Lexus for a written diagnosis , but was told not possible as sent to laptop when plugged in

That seems strange but there you go. Have you not got a laptop and Techstream yourself?

I'd still get the 12V Battery properly load tested first because that's obviously the cheapest option. If that's alright and the wiring harness and associated connectors are alright and it looks like time to replace expensive items, I think I'd be tempted to look on eBay/breakers for a cheaper, secondhand solution.

[AWF]

Over the last four years of owning my RX400 I have had quite a few odd error codes appearing . On each occasion it turned out to be the Bosch 12volt Battery I had fitted shortly after purchasing the car. The Battery was replaced free f charge by Euro Car Parts on each occasion. I use Toyotatech in Guildford to service my car and have found him to be very fairly priced and gives a full diagnoses without any bulls**t.  If you are not able to check your own Battery I would  get in touch with him and get your car to him. I have now replaced 12 volt Battery with one purchased from Lexus Spares Direct. All error codes cleared by Paul at Toyotatech and have not had any problem since. My money is definitely on the Battery.

[JRSM]

Herbie,

Thank you for your advice.

Kind regards,

James