Strange problem

[MLane]

Hi All,

Newbie here. I have a 2005 RX 400h with 193,000 on the clock. I have had a strange issue. When pulling up to a junction, braking gently, the engine "stalled" and the braking jerked, like some one had run into the back of me. The check VSC system light came on along with check hybrid system. The car then ran on Battery only for a short distance so I pulled over and switched off. I restarted it and then only the "check hybrid" light came. The car then ran as normal, using engine and Battery but with the engine management light on as well. After arriving home, I switched off and the started it again 5 minutes later and no lights were on and it ran normally. This happened last week and then exactly the same the other day. My "local" lexus dealer is closed at present and are booked up for all of May so can't get it looked at which is a bit of a worry as my mother is not in good health and I may need to help out and she is 120 miles away.

Has anyone had anything similar or any thoughts on what it might be.

Thanks in advance.

[Mihanicos]

Hi,

Before considering anything more serious and expensive, check that the 12v Battery is charged to a minimum of 11 volts. Do this after the car has been switched off for some time. When it falls below that, you get unrelated Diagnostic Trouble Codes on starting.

Another sign of a 12v Battery being on its way is when the car is parked, you start it, wait for the engine to stop, leave the ignition on and wait a few minutes. If the 12V Battery is below 11 volts, the engine restarts to charge it. The fuel consumption also increases by about 3 miles to the gallon or more, depending on ambient temperature and driving conditions.

Regards,

 

Chris

[MLane]

Thanks Chris. The Battery is only a few months old - it was replaced under warranty as the one I had bought from my local motor factors failed.

These issues are not just after starting so I don't think it will be the Battery. When parked, the engine only restarts when the hybrid Battery indicator drops to a low level which can be quite a while if nothing else is running.

[Herbie]

1 hour ago, MLane said:

These issues are not just after starting so I don't think it will be the battery.

Could be Battery connections though; those symptoms are often an indication of Battery and/or battery-related problems.

Disconnect the Battery and clean both the Battery posts and the cable clamps, as well as the other ends of those cables and the engine to body earth strap, then make sure to get a really good tight connection when replacing them.

17 hours ago, Mihanicos said:

Another sign of a 12v battery being on its way is when the car is parked, you start it, wait for the engine to stop, leave the ignition on and wait a few minutes. If the 12V battery is below 11 volts, the engine restarts to charge it

The Battery falling below 11V is not the only reason for the engine to fire up. The engine is the only source of heat for the cabin so it'll fire up as and when necessary to keep the cabin temperature up to whatever the system is set at.

You really need a multimeter to check standing Battery voltage against the chart below, then do a second check with the car in the READY state (the equivalent of having the engine running and the alternator spinning on an ordinary car), which should read about 14.5 - 14.7V if the charging system is working as it should.

If that doesn't sort it, the next step would be to get an OBD2 reader (or preferably a laptop with Techstream) to read any stored codes.

[MLane]

Thanks Herbie. I did give all the connections a good clean when I changed the Battery but will check just to make sure nothing has come loose.

Seems strange that the faults occured after around 1 mile the first time and after around 9 miles the second time.

I have been having intermittent power issues for a while - happens at odd times but often after sitting on the motorway in a 50mph zone with the cruise on - try to accelerate away at the end of the roadworks and it has the acceleration of a 2CV. The engine is revving but car is not matching it. No warning lights and no codes stored. I took it into Lexus Plymouth a few weeks ago and they checked it out and couldn't find anything. The technician came out on a test drive and I could not get the fault to occur - typical!

Hopefully, there will be some codes stored now so they can find a fault !! - when we get out of this lockdown!

Thanks again.