Replacing Ecu

[chrisnisbet]

I have a 95 LS400.

When the ECU is replaced, what procedure (if any) do you have to go through to get the originl keys to work with the new ECU?

I've tried a search, but don't seem to get any results. Is there something wrong with the forum search?

I seem to remember someone mentioning some procedure like turning lights on/off, doors open/closed, but can't find the topic anywhere. Not sure it applied to the 95/LS400 either.

[morg96ls400]

I have a 95 LS400.

When the ECU is replaced, what procedure (if any) do you have to go through to get the originl keys to work with the new ECU?

I've tried a search, but don't seem to get any results. Is there something wrong with the forum search?

I seem to remember someone mentioning some procedure like turning lights on/off, doors open/closed, but can't find the topic anywhere. Not sure it applied to the 95/LS400 either.

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I replaced the ECU in my 96 LS (same series so should be relatively the same procedure) and all I did was remove the old one, plug in the new one, and my car still unlocked with the same remote. I believe this is because the signal is stored in the transponder chip that is located on the driver side dash or somewhere on the driver's side.

In other words, the ECU does not need to remember the remote, just the transponder, so no programming is necessary if you only replace the ECU.

Hope this helps.

[chrisnisbet]

Hmm, interesting. I've got a problem with the car, and I'll describe it as it has been described to me by the dealership.

My car recently clapped out due to an ECU fault (code 28 from memory).

The dealer has replaced the ECU, but wasn't able to start the car because the keys didn't match the ECU. They are currently trying to find out whether they can program the ECU to accept the old keys, or whether I will need new keys that are matched to the ECU.

Personally, I can't believe that I would need to get a whole new set of keys to go with my ECU, but maybe that is some security 'feature'.

car came with a warranty, which covers most of the cost, so I'm not too bothered, but it is taking a very long time to get my car back.

Four weeks so far (waiting for ECU to arrive mostly).

Bit disappointing that it has taken this long to get the car fixed up I can tell you.

Also a bit disappointing that they don't really know how to get the car going again.

Maybe they haven't replaced too many ECU's.

[95LS400Bob]

I replaced mine in my 95 and fired right off no problems. No programming.

[chrisnisbet]

Just heard that they have the engine up and running again. That's good news. They're changing the ignition rotors now. I have to wonder if that is where the main fault lay. I wonder how often the ECU on these cars actually develops a fault.

[nc211]

Quite a few of these models have faulty ECU units, but most people don't know it. It's usually tied to a bucking feeling around 40mph, and the car stalling after a long road trip. I have a 95 as well, and my ecu unit was replaced by the dealership too, under their 90 day / 3,000 mile warranty. It didn't take them but 4 days to get it done, and there was no mention of needing my keys. If I recall, the transpoder chip did not arrive to the lexus keys until the 1998 model.

[chrisnisbet]

well, my car had the 'stalling after a long trip' problem, so I'm hoping that the new ECu will sort that out. The dealership said that the ECU for Singapore models is quite different from the U.S. ones though.

The orignal problem I had was that the car just dropped into limp home mode, and the diagnostic tool indicated that I had faulty O2 sensors, and a faulty ECU. Warranty has covered most of the cost, so it isn't going to cost me too much. They didn't tell me how they got the key working with the new ECU. I'll ask today when I pick the car up.

[nc211]

Some of the guys with the stalling problem were able to fix it with the cleaning of the throttle body assembly with some carb cleaner. I haven't had that problem yet, but my intake is pretty clean. I just had the herky-jerky off throttle shock problem.

[GRAND_LS 4]

Some of the guys with the stalling problem were able to fix it with the cleaning of the throttle body assembly with some carb cleaner. I haven't had that problem yet, but my intake is pretty clean. I just had the herky-jerky off throttle shock problem.

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Transponder keys didnt exist until 97, so the 95's only had to worry about getting the physical key to match.

[chrisnisbet]

hmm, wonder what they were talking about then if the transponders didn't exist on the 95's.

[pkshin]

I replaced mine in my 95 and fired right off no problems. No programming.

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At what price did you replaced and where?

[UCF3]

yeah, the chip in the key wasn't put into service until the 97 model year.

chrisnisbet:

What's wrong with your car? from the sounds of it, your ECU wasn't updated, but what else did the dealership say was wrong with your car?

[flash213]

Sounds like you may have a shady dealer on your hands. I replaced my ecu and faced no prblems after install. That was back in April and have had no problems since. Good luck to you.

[chrisnisbet]

Nah, I think the problem may have been just that they weren't that familiar with the car. As the car was under warranty, I didn't have to fork over any money. Anyway, all seems well at the moment, since the ECU change. Haven't been on a long trip since then though...

[nc211]

Funny this post came back up as I was thinking about it this morning on my way in. I remember when my car was having it's ecu replaced at the dealer, they called me too requesting the master key to set the ecu unit. I was out of town at that moment and told them I can't get it to them. A couple days later, they called and said the car was ready to go. So, yeah, I think they get stumped on the model year and keys.

[oohryry]

Quite a few of these models have faulty ECU units, but most people don't know it. It's usually tied to a bucking feeling around 40mph, and the car stalling after a long road trip. I have a 95 as well, and my ecu unit was replaced by the dealership too, under their 90 day / 3,000 mile warranty. It didn't take them but 4 days to get it done, and there was no mention of needing my keys. If I recall, the transpoder chip did not arrive to the lexus keys until the 1998 model.

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You've got to be right. They told me at the body shop in the dealership that I have to get a new ECU to buy a new key with the remote. I plan on doing it soon since they said Lexus will pick up the charge for the new ECU. They must know the ECU were faulty but don't want to take the blame. Anyway, the key is $300 dollars. I'm willing to pay that to get a 1500.00 ECU replaced which is probably faulty in my LS also.

[pacolet]

Sounds like you may have a shady dealer on your hands. I replaced my ecu and faced no prblems after install. That was back in April and have had no problems since. Good luck to you.

How much did you pay for your ECU, source?

[sonyman]

Could someone post a guide, preferably with pictures, on how to change the ECU in a UCF20 LS400? I had no luck on getting Lexus to change mine for free so I'll have to do this myself.

Scott

[mann777]

I had the same problem with the ECU and the door key not in tandem with the ECU program. While on warranty they replaced the key and the new ecu itself, i think if under warranty you can ask them to replace. They did take 23 days for mine as the ECU itself was not in stock with the dealer. They were coughing up a story that it is been imported from Japan and already been shipped. So here goes you would have another wild story. The ECU is placed below the glove compartment, Before removal the battery negative terminal removed prior to disconnection. It is a expensive affair if you have to shell out for a ECU, but again you should get the right ECU serials as per the model / year of the car. My suggestion is stick with the dealer and get them working, no matter how long it takes. Also just a suggestion try suggestin this one The ECU stores certain codes for the Theft deterent system. They need to erased completely and they can be only done thru the OBD tool scan which the dealer has. Some dont need to be done they just sync with the new ECU.

cheers

[mann777]

geese sorry folks this is left intentionally blanks..............finger probs