Lavrishevo

iTrader: (1)

I have a coworker with a 1995 SC300. He installed an engine and manual 5 speed transmission from a 1997 SC300. He has a rebuilt ECM in the car from a 1997 GS300 I believe. I know, I know... I was in disbelief myself. Anyway, the car runs but is getting terrible gas mileage and runs a bit rough. We are unable to read the codes. It is connected to the OBD1 port but bridging the pins does nothing. Maybe an ODB2 port needs to be wired in. Anyway, I'm just trying to help him read his engine codes. Any ideas...

99SC42

iTrader: (44)

First issue, there is no 97 GS300 in the US, GS300 was never made in the SC300.

You need a 97 SC300 ecu to fix the Problem.

You cannot read the codes using the 97 ecu and harness on obd1 car unless you use the 97 sc300 dash harness, I found that out the hard way, took me a month... to figure it out but at the end I just grabbed a 92 sc300 harness, ecu and maf sensor , Problem solved.

I can help you figure it out, but I will need more info from you.

Lavrishevo

iTrader: (1)

Maybe the ECM is from the 1997 SC300 not the GS then. I'm not exactly sure. Just going off what I was told.

KahnBB6

iTrader: (5)

Since it's a 1995 OBD1 chassis and the 1997 engine and transmission are almost identical to the 1992-1995 and 1996 engine and transmissions, I'd think the better solution would be to locate a 1992-1995 SC300 5-speed or 1993.5-1995 Supra NA 5-speed 2JZ-GE ECU and swap that in.

Using a 1997 GS300 ECU is bonkers-- it's not calibrated for a manual transmission in addition to not communicating with the OBD2 harness correctly.

99SC42

iTrader: (44)

^^^ One Last time there was no 97 GS300 offered in the USA.

Last year of the first Gen GS was 96 and first year of the 2nd Gen was 98.

The 96+ SC need 3 oxygen sensors the last one is on the midpipe, where the 92-95 only has 2 sensors, the 96+ needs that 3rd one or the car will run like crap.

Ali SC3

iTrader: (10)

you can wire up the obd2 port straight to the ecu or reusing the obd1 port wires but it might be worth it to just grab an obd1 harness and ecu.
You can even use an obd2 harness with an obd1 ecu if you rewire the maf, but getting both obd1 harness and maf is ideal.

this page shows how to do it on a supra to get an obd2 port working with an obd1 body harness.
http://www.supraforums.com/forum/sho...2-ECU-Upgrade&

KahnBB6

iTrader: (5)

99SC42, I wasn't attempting to upset you. I was only trying to help the OP. After seeing your post I became honestly curious and looked up the GS300 for model year 1997 in Carson Toyota's parts system and Sewell Lexus' parts system. Both show a 1997 Lexus GS300 was available, at least in 49 states and I assume CA too. What am I missing here?

http://www.trademotion.com/parts/199...15&searchText=

http://lexus.sewellparts.com/parts-c...S300-1997.html

99SC42

iTrader: (44)

I'm not upset here we are cool buddy!!

Ali SC3

iTrader: (10)

late model 96's are technically 97's, but the gs300 was not produced in 97. the ones made late 96's were sold in 97. new vvti ones werent made till late 97 which are technically 98's. sometimes they sort of take a while to jump to a new body.

http://en.wikipedia.org/wiki/Lexus_GS#1991.E2.80.931997
"Additionally, more powerful V8 sport sedans provided strong competition. By 1997, the price of the GS 300 had risen to US$46,000. Production of the first generation GS sedan ended in late 1996"

99SC42

iTrader: (44)

Thank You

OP please post the pics of the part number of the ecu, pics of the maf sensor, and hopefully we can help you out.

One of the issues is the 3rd oxygen sensor. the 97 ecu needs a 3rd one under the passenger seat and it plugs on the dash harness on the side of the center console.

Ali SC3

iTrader: (10)

yeah he probably has the whole 97 ecu and harness. its really not worth using that ecu cause it will throw codes for missing the second crank sensor. it will still drive and all that but I would just sell it and get the parts from a 92-95 sc300 matching harness and ecu.

we could tell you how to rewire the 97 stuff but most people dont want to mess with it. if you do go ahead with that then just post questions in here.

99SC42

iTrader: (44)

Ali- I went through the same crap when when I was selling my 93 sc300 with 97 swap in it, over a month of hard diagnosis, I just gave up and installed a 92 ecu, harness, maf and never looked back.

I tried jumping it right at the ecu to get a code and no luck, it wouldn't work..

Ali SC3

iTrader: (10)

makes sense. even when you know what to do there are always issues you are right its not worth it. we all know what I would do obd1 harness and 2jzgte ecu =)

if it is running you don't have to read the codes to tell whats wrong with it though. just check over the basic stuff and if you have never done the o2's then do the o2's you cant just wish good gas mileage everything has to be working well together.

KahnBB6

iTrader: (5)

Ali and 99SC42, thank you! That completely explains it. It makes me wonder if the SC series was affected as well (and that might also explain the carryover drivetrain with new body and why only 120 manuals were sold that year as the option was being phased out). And 99SC42, we're absolutely cool! I had honestly never heard of this leap year for the GS or any other model (other than the '96 Supra TT 6-speed and Federal-only '98 Supra Turbo).

As to the OP's issue and both your comments above I agree. The 96-97 ECU requiring the missing crank sensor makes sense. He needs a 92-95 ECU, preferably the M/T version. Bad O2's could also be the issue and are an easy DIY 15 minute job if mileage on them is unknown. Also the distributor cap, rotor, plug wires and spark plugs.

That third O2 sensor also exists on Cali SC300's of all years (but not Federal cars from 1992-1995). My car has one. It doesn't affect fuel economy, however.

Lavrishevo

iTrader: (1)

Thanks guys. I will pass this on to my friend. Honesty, once he told me how convoluted everything was and that we can't get any codes I kind of backed off.

Overall, the car runs kind of bad. Terrible gas mileage, sometimes difficult to start, his car smokes a bit on startup too. He also put some headers and an exhaust system on. Anyway, I will take some pics of the part numbers and maybe make a video of how it's acting next week. Thanks again for the advice.