New battery, then ECU problems...

[Toni Rauch]

I own a 2002 IS300.

I had a Battery failure, so I got a new Battery. Since then, the following yellow lights always came on (not flashing), on the dashboard - engine warning, oil warning, failed light bulb. In addition, the small dial indicating miles per gallon has stopped working.

I tried resetting the ECU by disconnecting the negative side of the Battery for an hour - this didn't help. So I removed the EFI and ECTS fuses for a couple of minutes and then reinserted them.

The engine warning yellow light is now off but the other two remain. The MPG dial still doesn't function.

I have plenty of oil in the engine and cannot find any lights/bulbs that need replacing.

Before the Battery failed, there were no problems at all. "...a hell of a coincidence....?"

Any ideas or help will be appreciated....

Thanks!

[ColinBarber]

I suspect you have a blown fuse or two. Something like the MPX-B or Gauge fuse, but check all of them, engine bay and cabin fuse boxes.

[JayZuuk]

Didn't want to start a new topic with this being on the first page but if I need to start a fresh one just let me know.

Recently whilst driving the ECU came on, ordered myself an OBD scanner which displayed P0155 - O2 Sensor Heater Circuit Malfuntion (Bank 2 Sensor 1). Was planning to look at how to fix/test this next weekend when i'm off however after finishing work last night and starting the car I have encountered the same issue as OP.

Tachometer didn't budge, MPG not reading, oil light & rear light all happened at the same time. So I did some searching last night and this morning coming across a few posts of the same issue. https://www.my.is/forums/f115/tachometer-problem-437096/ this one having the most discussion/related information to my issue.

I double checked the oil this morning along with all rear lights, everything spot on. I double checked the ECU, still only showing P0155. The negative Battery terminal was looking pretty nasty so I unhooked it all, cleaned both terminals and connectors then threw it all back together. Still having the problem but of course the ECU etc was wiped, so I'll have to wait for the code to come back to fix that sensor fault. Went round and checked the fuses, all looks fine, nothing black or blown. Decided to check tachometer again to see if one had come loose or anything.

Success! or so I thought for 5 seconds, now when I start her up the tachometer works, I have no oil or rear light error for all of 5 seconds then all three die/display on me. Shut it down, tried again this time giving a solid rev but same thing happens. I've checked the volts at the Battery, giving 11 turned off and 13 after starting up. Hopefully someone can give me some advice on what to do next, i'm fresh out I think now. Need to fix the inside driver handle yet too 😅

[Herbie]

Probably duff Battery if it really is only reading 11V

 

[JayZuuk]

Ah that's a great table! Thanks, i'll ask around and borrow a second meter soon as I can to double check and post back.

[Texas]

Any fault finding on modern cars with masses of electronics and errors coming left right and centre gotta start with a sound Battery, you be amazed what errors can rise up when voltages are not perfect!

My daughters Fiat 500 was throwing up " Have Power Steering Checked" after every start up, turns out the electric power steering won't operate below a certain voltage ( defaults to manual steering only but not the end of the world in a Fiat 500!) and the Battery would just dip below this threshold after the starter motor took it's portion!

First plan of attack gotta be sound Battery and start afresh, if problem is in fact an O2 sensor then it will rear it's ugly head again.

paul m.

[JayZuuk]

Bit of a weird report but I decided to order a multimeter instead of trying to borrow another one. Turned up after I had to leave for work yesterday unfortunately so drove to work, tachometer didn't even work for the 5 seconds. Got to work, turned off and back on, worked for 5 seconds. So i'm leaning more on the Battery as suggested. Drive home, tachometer works and no oil or rear light bulb lights....all the way home.

Left car as is, didn't manage to get round to checking the Battery before work so left for work and yet again tachometer works all the way there with no oil or rear bulb lights, however the ECU comes back on. Nipped to the car on my break, Battery showing 12.4v turned off on the new meter, okay so the Battery seems fine, kept it connected for starting up and slowly turning on multiple things such as lights, ac, seats etc and it was all fine didn't drop too low for CCA on start up either, tachometer working again whilst doing this.

Poked around the engine and noticed that one of the connections for the driver side radiator fan was hanging loose, no idea how or why, plugged it back in reset my ECU on the small chance it's setting off my code somehow. Not had any of the lights or issues on the way home, so I literally cannot say what has caused the issue or fixed it, the ECU i'll have a better idea of in the next day or so but right now i'm more confused than when I started!

[holiday]

We have a 2014 CT200H and we are currently having a similar issue. The story begins like this we were on holiday for 2 weeks and came back and the Battery was dead. Rang up lexus roadside assistance and the AA came up and did his tests. Car came alive but didn’t shift to drive went through the diagnostics on his tablet and didn’t work. Informed us that the flatbed lorry would come on Monday morning which was fine. AA van came on Sunday night and informed us that storage facility was full. So on Monday morning the flatbed came again and informed us that a 2 man team was required as the car couldn’t start and had to block off the road. Car went to the lexus garage and Tuesday started the diagnostic process again. Found out the Battery died. We authorised the change of Battery but still couldn’t shift to drive. So they did diagnostics again and couldn’t find the fault. Lexus compass had to be involved and found that the transmission ECU failed on Friday. So hopefully tomorrow (Monday) the part should arrive but they still wouldn’t know if it will work. Will keep you posted.

The cost of this Saga is currently going into £500.