Largo

Hi All,

I have spent numerous hours here researching my problem but can't seem to find the answer.

My 2004 LS430 trunk latch cycles 5 1/2 times every time I open the trunk regardless of the method I use to open it.

It appears to me that the ECU is not working correctly.

The Luggage Compartment Door Opener switch under the steering wheel tested fine. The Luggage Electrical Key Switch on the right trunk tested fine. The Luggage Compartment Door Key Unlock Switch (Key Lock) tested fine. The Luggage Compartment Door Striker Assy switch tested fine. The Luggage Compartment Door Closer Assy (Trunk latch and motor) all tested fine and I even swapped the trunk latch from my wife's LS430 to mine to make sure.

So I next tried to find the Luggage Room J/B ECU. Under the removable felt panel inside the trunk on the drivers side I found the Luggage Room J/B but I can't locate anything that looks like an ECU.

The diagram I found for a 2002 J/B looks identical to mine. I see several connectors for wiring harnesses, noise filter, 2 relays and a dozen fuses but no ECU.



A trip to the dealer parts department was no help but for $141.00 (1 hour) he was sure the tech could find it.

If anyone could point me to the ECU and/or part number I would be grateful.

Tom57

The J/B in the trunk is the ECU. It is the fuse box, and it has internal components which control some function of the vehicle. The driver and passenger side J/B near the footwells are similar (both J/B and ECU combined).

Largo

Ahhh, I see.

So if it is the ECU functionality that is a problem then I may have to replace the whole fuse box?

Dealer list $910 without shopping around.

Thanks for that help.

Tom57

Yes, IF it's the trunk J/B, then the whole J/B should be replaced since the ECU is incorporated into that J/B.

I've seen that trunk J/B at parts recyclers on eBay. You should be able to purchase used for less than $200. Find the part number at an online Lexus parts dealer such as: http://www.lexussouthatlantaparts.com/ See diagrams. Use part number for search online (eBay) for used part. That's a straight-forward DIY.

rkw77080

Some of the luggage opener/closer functionality resides in the driver-side JB ECU. Attached are pages from the repair manual - happy reading...

Tom57

Largo, rkw77080 is your best friend here with diagrams for every repair. The driver side J/B ECU is also typically available at recyclers, including on eBay.

Largo

Thanks for the help.

I'll swap the parts from my wife's LS430 to test.

Lavrishevo

iTrader: (1)

I seriously doubt it's the trunk ecu. I bet it's the lock mechanism itself. Far more common of a failure. Mine was also replaced under warranty years before I purchased the car. Might be more common in 04 models. Faulty position detection switch sounds like a good theory.

Largo

I doubted it was the ECU too.

That's why I swapped a working trunk latch and motor from my other LS430 and still have the same problem.

The symptoms point to the OPN internal switch not working but that tested fine then I opened up the latch assembly and cleaned the contacts for the OPN/CLS switch, then I switched the whole assembly out.

My next step is to look at the ECU/connections to see if anything odd and then I'll swap the ECU/fuse block.

It's been a frustrating journey. I am amazed at how complex the trunk latch is with all the switches involved.

Lavrishevo

iTrader: (1)

Oh. So you swapped the whole assembly. I did not understand that. I guess it did say that in the first post. Well, sounds like you are on the right track. The issue my car had was not the same. From the tech notes it had to do with the trunk not staying closed. How are your trunk seals? Any sign of cracking or deterioration that might allow water in the trunk?

rkw77080

Can you elaborate on "cycles 5 1/2 times...", especially the "1/2" part?

Does you trunk latch cycle rapidly (machine-gunning)? If so, it may be caused by a bad (failing or sticking) relay - see circled in red below... Unfortunately, these relays are part of the ECU.

Tom57

Those relays may plug into the side of the J/B as they do on the front driver and passenger footwell J/B ECUs. There are part numbers on the relays that plug into the front footwell J/B ECUs.

Largo

I tried to swap the J/B ECU from my wife's 2002 LS430 but it is a different part.

I ordered a used J/B from Lithuania, installed it today and voila, trunk works fine again.

I tried to get into the guts of the ECU to see and maybe fix it but I couldn't figure out how to do it. I removed the screws and the it has plastic tabs but there was one spot holding the circuit board that I couldn't get to release. I saw corrosion so I was pretty sure that the J/B ECU was my problem.

Thanks again for the help.

heartygrn

Thanks for this thread. Mine has also gone wonky on my '04 and I replaced the motor (64650-50020) and it behaves the same way so now I will replace this trunk junction fuse box (82670-50080) and see if that fixes it. I ordered one from Malaysia so I will update when it arrives. Funny thing is it works fine in the summer but it's been getting worse each winter. As I raise or lower the trunk lid the motor will start firing randomly at various positions.

heartygrn

Replacing the trunk junction fuse box did not fix the problem. I think there is some switching going on in that retractable wire housing on the left. If I hold that wire and don't let it retract the motor does not go crazy. I'm thinking I'll open it up and see what's going on inside.