NickySB

Been back to fault-finding-ville today! Checked the 12v power had enough voltage, checked the IGCT2 fuse , all ok, so went into the U0110 fault finding. Got all the way to the last step without anything concerning flagging up. The last step requires an oscilloscope which I don't have to hand at the moment. I'm not sure the fault finding will actually help in this instance as the car wouldn't start before I replaced the inverter and had slowly slipped into this degraded state. Possible that another fuse was slowly going or alike. Might have to investigate all the potential fuse options. I've no reason to suspect the hybrid battery fuses (SMRG & SMRB) but I suppose anythings possible. I feel as if I'm chasing multiple faults, be that from the welding incident or before.

I've replaced the inverter, checked it all over, turned it on and I now have the usual 'Check Hybrid/VSC/EB*' - read the car with Tech Stream and I've got 2 new codes - P0A1B-788 & U0110-657. I didn't have these codes before I replaced the inverter. I wasn't convinced by the inverter as the scrap yard didn't prevent the excess coolant coming out, so it was wet when I unpacked it. I dried off as much as I could as let it air dry but not convinced its good. The joy continues.....

The car degraded again the next day and wouldn't give me the 'READY' light on the dash. Tried removing the fuse and no dice, so looks like I need to replace the Inverter again!

Thanks Robert - however sadly I celebrated too soon! After driving the car the day after without issue, I went to it yesterday and the arrows had gone again but it would start and drive. I've then gone to it today, and it won't even give me a ready light - the dreaded P3108 has returned, and this time P3000 (battery control system) has also appeared. My immediate suspect is the inverter but more research required. My car is the gift that keeps on giving! I think its just out to defy the Lexus reliability reputation! 😒

Thank you, yes, absolutely bl00dy elated 😁

IMG_9595 2.HEIC

FINALLY FINALLY FINALLY RESOLVED! FFFFFIIIIINNNNAAAALLLLYYYYY 🥳 Replacing the fuse has bought the arrows back and removed the P3108 code - let joy be unconfounded. 😁 I'm off to dance around the driveway!

Thanks BigBob that's useful to know, it's interesting the Lexus Manuals don't ever end up at considering the Inverter, all roads in the manual lead to compressor, harness or ECU.

Code is still present, and Inverter water pump is functioning without issue.

Spent another day fault finding. I’d studied the wiring diagrams as a whole a bit more and realised that the A/C W/P fuse / relay is not for the inverter water pump, it appears ( based upon the LS interpretations) that the A/C W/P refers to the A/C system not the inverter water pump , which is appears is covered separately. With that in mind I checked the fuse for the Inverter W/P and it’s perfectly fine. Started the car with the fuse removed and found no change to the arrows. I’ve tested the pump separately with tech stream , and it commanded it on/off, but I didn’t check to see it was actually moving the water around so will retry that today. I moved my attention to the hybrid ECU connector as I’ve noticed that 2 wires ( a brown one and a yellow one with the yellow one being the D out connector) are somewhat proud from the rest of the wires. They appear to have been yanked at some point. Found out how to release the pins and checked them out , the yellow one was definitely stretched so I rewired and reconnected it, the brown was reseated and all seemed well. Sadly no change though when reconnected. I was convinced that would have some effect but nothing seen thus far, although I’m yet to read the codes again just to double check, so another job for today. The top yellow connector in the picture is the ETI (which goes to DOUT) removed from the ECU , the bottom one is a comparison from another donor ECU connector to show what it should be like. I want to try a different HV cable from the inverter to the A/C compressor just to rule it out. I’ve started accessing the inverter but noticed the HV fuse within the inverter (that sits above the HV A/C comp cable & frame cables) appears to be missing. I’m not sure how there’s such little effect on the car if it should really be there. I’ve never removed it myself, but if the missing link is the cause it doesn’t quite add up as the problem started with the engine change ( or certainly the missing arrows did, can’t speak for p3108 as I didn’t get tech stream until about 8 months later ) & the inverter being blown up was around 6 months later, which resulted in a changed inverter. The search for the return of the yellow/orange/green dashes continues………

Well I clearly have a gremlin running around my electrical system as the situation changed AGAIN! I spent a several hours yesterday checking various connections on the car. I found as follows: Inverter water pump connector has full voltage across it (my 12v was a little down after all the testing but it was putting out the same - 11.39v) The A/C WP relay shows 9v dropping to 5v when ignition turned on The IGN & GRD connector for the A/C compressor shows good voltage 11.3 Output at the passenger cabin fuse box for the A/C WP showed 10.10v Hybrid ECU DOUT line showed 0v Compressor DOUT line showed 0v The fuse box connector, which plugs into the row of pins which form part of the hybrid ECU hardness (as circled picture above) had good voltage too (11.3v, 78 ohms) The A/C WP connectors also have good resistence.

Transpires the fuse isn't actually blowing (the way its made it makes its look as if the link has blown and dropped to the bottom but the link is actually intact). More testing.....when checking the voltage either side of the fuse I have 12.8v one side and something like (from memory) 0.1v from the other which is as expected. I was suspecting issues in the fuse box given the welding incident, as the radio decided not to switch on for reasons unknown the other day (& radio fuse 3 is in the adjacent slot to the inv w pump) , but it was then fine after a power cycle, the other fuses & voltage checks seem to be ok. I bought an open/short circuit tester which seems to indicate issues in the DOUT link around 20cm from the ECU, however checking the wire (After cutting open the harness protector) around that point shows no difference in resistance. I've not checked the voltage because if the voltage at the connector is dropping, and the ECU connector, and the fuse box, i'm fairly the happy the cable in between wouldn't be at fault as the voltage drop is being seen both sides. I've tried disconnecting the inverter water pump and no change to the readings. Next steps are : check compressor to ground in more detail check the G/Y between the hybrid ECU & fuse box (as per wiring diagram) check voltage / resistance/ground at the inverter water pump check voltage supply cable between fuse box and i.w. pump and check junction boxes Replace HV line between inverter & compressor, just to rule it out Try to check the inverter connecter with the open/short circuit testor Confirm inverter fuse is in place and and in good condition.

More fault finding.......after yesterday yielded no results I thought about it overnight and decided to try and trace where the reduced voltage is originating from. Testing the voltage between the A/C Compressor D Out pin & the ground shows degraded voltage. Doing the same on the ECU ETI pin shows degraded voltage. Going further up the circuit , I testing the pin at the fuse box junction connector, same there. This ruled out the harness, as the harness starts at the fuse box tray which said junction connector goes into, before going to the ECU's and all around the engine. Looking at the circuit diagram the only thing in the circuit before the junction box is the 7.5a A/C W/P fuse. It looked completely intact, but a resistance check gave off poor results. I replaced it and it blew as soon as the ignition came on. Although this doesn't resolve, it is at least narrowing it down.

The second hand unit changed nothing, so the problem has to lie elsewhere. I tried running 12v direct to the D-OUT wire but no change.

Reviewing my options I decided to disconnect the AC compressor connector (6 wires) and go for another drive, this time no hybrid issues (30 mins driving, came on yesterday after 15 mins) so perhaps it is JUST the compressor again - but lets see when another 2nd hand unit arrives.