alexchris1

Hello everybody, i need some help regarding a Lexus Rx450h with the C1378 error.
This code popped out right after a check hybrid system, the error for the check hybrid system was:" lost comunication with hybrid battery suply (029a-123)". I reset this code, managed to arrive home with the car and then the C1378 code start popping up along with the check brake system in the dash.
I checked the fused, i checked the brake power supply and the harness, at this point i do not know what to do anymore. I tried resetting the car by unplugging the battery and using a paper clip for the 13 4 pins in the obd... still getting the error.
The cars abs esp, tcs, etc work fine, i tested them but the error is still present. At this point i do not know what to do anymore. From what documentation i found on the web, the skid ecu could be the problem but what bugs me is that all the safety functions are active and working properly.
Can someone help me what to do?

Thank you!

Clutchless

https://www.google.com/search?newwin...63.lssQ4dT2pWg

This may be expensive.

Droid13

The brake power supply is not as expensive as replacing the wiring harness (almost on the point of being reasonable for a hybrid specific component). You've said you've tested it but since I don't know what's involved with testing it, if this was my issue I think I might try replacing the brake power supply. Unless something was obviously damaged, I tend to believe if a problem presents itself that could be related to a capacitor/power supply, a wiring harness, or a circuit board, the power supply is going to be on the top of my suspect list.

alexchris1

Replaced the bcps, still getting the error. I do not know what to do at this point

Droid13

I'm not sure about the paper clip in the ODB connector thing to reset, but have you tried just clearing the code. Is the code "current" or "history". Sometimes when a system error occurs and the code is logged, even fixing the problem will not clear the code. After a particularly rainy and windy night, my RX "check hybrid system" warning went on, and threw a code for the transmission cooler pump (which are apparently a little susceptible to water issues when they get older). Several functions stopped working but I got home ok. Next day everything was back to normal but the check hybrid system warning persisted for a week. I finally hooked up my lappy and cleared the code (which was in history, not current), and since then all is normal.

Another thing, not trying to second guess you too much, but double check the fuse.

I am curious about other comments you made, does the vehicle drive normally otherwise?

alexchris1

The vehicle drives perfectly fine, the cruise control system does not work. I tried deleting the error with techstream but i can't, it is permanent. I tried the paper clip also.. nothing. I rechecked all the fuses today, everything is ok. I will check again the bcps.


Thank you for your answer

salimshah

The P codes mostly are accumulated error codes, and tend to go from none to pending to set. Where as a C code is a hard set/unset value so a clear won't do much as the set will happen instantly.

I would also suggest, that check the 12v battery health.

Salim

alexchris1

Well... finally, problem solved! Man this was a tough one. Ok so apparently the problem was with a connector at the driver side,(mine is LHD). In every documentation of this problem that I had it did not tell anything about the driver side connector. I took of the panel of and apparently a blue plug right at the bottom was the cause. I had a friend who is an expert with electronics and after hours of testing saw that the harness is in short and traced a light green cable that was the cause. Then we traced the wire to the drivers side and managed to sort out the problem. Hope my experience helps others if they encounter such a problem.


The trace was even harder when the diagnose (techstream) pointed the BCPS as being faulty (error: c1378, sub code: 112).


Again i want to thank you all for helping me with opinions. So happy everything is ok now.

Sami3

2 monts ago i bought Rx 450h 2010 from Sweden. I live in Finland btw...

Few days ago "check brake system" light went on. Today i took car to a Toyota-service and had codes C1378 and C1A50. Now i would like to know where this connection locates that you were talking about?

In engine room and drivers side but where exactly?

Best regards,
Sami from Finland, near Artic Circle

alexchris1

On the drivers side near the park brake pedal there is a plastic panel where are some conectors, pull the plastic cover out of the way and look for a blue plug. That was my problem.
I believe yours has a problem with the radar cruise control that is linked with the vsc module that is located on the passenger side footwell.
Check the subcodes for those errors with techstream and take it from there.

riredale

Alex, I want you to diagnose my RX450h if/when I run into weird issues!

Sami3

​​When i turn power on i can activate cruise and there is text "radar ready". I can also activate cruise without radar option. When i go on the road and speed raises up to 40km/h monitor shows "check cruise control". But in both options, i cannot set speed on 0-40km/h area. Hope you understood, my english is not perfect...

salimshah

Cruise has a minimum speed, below which it can not be activated ... and my guess is that it is 30mph.

And your English is fine, dont worry about it. If you must we can poll to se how many members can communicate in your native tongue.

Salim

Sami3

Thanks for reply Salim!

At this moment there is nothing much i can do to fix my car. I dont have Techstream etc. yet, but im gonna get it. Btw, my friend has a Delphi codereader. Is it ok for Lexus?

I would be very pleased for all information i could get here to fix the problem!

Kiitos! (Thanks!)

alexchris1

We need to check the subcodes specially for the 1378 error and see what the problem is. The radar cruise does not work if the C1378 error is set.
For starting point, open the panel next to the passenger footwell, and check if there is moisture or damp, maybe there is a connection problem. Then check every fuse. The ones in the trunk, on the 12v battery and then in the engine bay.
@riredale: If i can help, with pleasure.