C1377 code and flat battery RX400h

[Davey Blueeyes]

I'm getting this code after a flat Battery, due to lack of use. Am I just hopeful they may be related?? 

Or is it likely to be something more serious?? 

[NemesisUK]

Seems to be the capacitor for the brake control. Quite probable it's simply discharged due to the flat Battery

I'm sure @Britprius will be along shortly.

https://www.engine-codes.com/c1377_toyota.html

Toyota DTC C1377 Question

 

[Davey Blueeyes]

Thank you, I appreciate your input. 

I also now have the alarm going off intermittently while the car is running! It's funny but also annoying. 

Could a new Battery solve these issues? Yes, I'm an optimist! 

Thanks for your help

[Mihanicos]

Hi,

C 1377/43  relates to the brake control power supply,  a capacitor, which is used as auxiliary power supply for brake control when the 12v Battery is low.

If you scan the brake system, you should be able to retrieve further information codes which pinpoint to the source of the DTC displayed.

101 indicates deterioration of the capacitor and should be replaced.

102 indicates self discharge ie leakage of the capacitor.

105 indicates malfunction of the charging circuit.

This capacitor you should find  between the roof and the headliner above the rear seats.

 

Chris.

[Davey Blueeyes]

1 hour ago, Mihanicos said:

Hi,

C 1377/43  relates to the brake control power supply,  a capacitor, which is used as auxiliary power supply for brake control when the 12v battery is low.

If you scan the brake system, you should be able to retrieve further information codes which pinpoint to the source of the DTC displayed.

101 indicates deterioration of the capacitor and should be replaced.

102 indicates self discharge ie leakage of the capacitor.

105 indicates malfunction of the charging circuit.

This capacitor you should find  between the roof and the headliner above the rear seats.

 

Chris.

Thanks for this Chris, it's very helpful.

As an aside my OBD device is fairly basic. Is there a better one you'd recommend that isn't a professional level bit of kit?

Also any thought on why the alarm is going off intermittently?? Or how I disconnect it! 🙂

Thanks for your help, I really appreciate it

[Mihanicos]

Hi,

The position of the brake control power supply I mentioned is for a lexus gs 450h and it is located somewhere in the floor of the boot and not where I mentioned earlier. I had a better look at the location of the parts diagram. For your car it may be elsewhere. 

Check that your 12v Battery does not fall below 11v. If it does, to verify the fault use another good 12v Battery temporarily. 

If the Battery is not the problem, then there are various measurements you have to take to locate the fault. The information codes retrieved by a scanner will be a guide how to locate the fault and subsequently repair it using the repair manual. I don't think that you can disable the alarm because the brake system is quite complicated on Lexus hybrid models and it is a matter of safety above all.

As far as scanners are concerned you can find a few on eBay, including the Techstream which offers dealer level diagnostics.

 

Chris

 

 

[Davey Blueeyes]

Thank you, that's amazing! I really appreciate they are clearly different problems but I'm hoping a full charge on the Battery overnight will at least shut the alarm off! Not sure how to tackle that just now. 

Interesting that the only fault code showing is the C1377 one, alarm seems fine! 

[Mihanicos]

When the 12v Battery is below 11v,  you get totally unrelated codes. When my 12v Battery was low I used to get " Variable gear ratio steering " the car would not start first time but on the second time I pressed the power switch etc.

Chris.

[Davey Blueeyes]

50 minutes ago, Mihanicos said:

When the 12v battery is below 11v,  you get totally unrelated codes. When my 12v battery was low I used to get " Variable gear ratio steering " the car would not start first time but on the second time I pressed the power switch etc.

Chris.

Thanks Chris, much appreciated. A new Battery is going on and we see how we get on.

Thanks for your input

David

[Herbie]

This may help a bit:

And here's where to find the Brake Control Power Supply:

 

[Davey Blueeyes]

Thank you Herbie! That's awesome

David

[AWF]

Recently laid up for 3 months with a broken ankle. when tried to start my RX 400 Battery was totally flat, zero volts, would not take a charge. Returne,d it to EuroCarParts under warranty who replaced it foc. When car restarted had all sorts of flashing lights on dash. Found a local Local garage specialised in Toyota / Lexus. He ran diagnostics which showed problems in every area of mechanics and electronics. Cleared all he codes only one reappeared, ABS sensor fault, broken wire on sensor. 

I say don't panic, get codes cleared and start again.