Check Engine Light - Fault Reading

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Gregor_99
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Check Engine Light - Fault Reading

Post by Gregor_99 »

Hi all,

My 1992 3SGE MR2 has a check engine light, and has done since I brought it. However I cannot seem to get it to display any codes after bridging the E1 and Te1 on the diagnostice port, the check engine light just stays on and doesnt flash at all. I have checked to make sure there is continuity with a mulitmeter, also checking to see the voltage difference between the two which is 5V consistently.

The car does have issues, as it does not like to rev especially when cold. As well as having very little power when driving.

I have had the ECU out and checked for leaky capacitors etc, I have attached three images below. One of the ECU cover and two inside the ECU. The ECU Part No is: 89661-17370 (Not very clear from picture)
IMG_0736(1).jpg
IMG_0693.jpg
IMG_0694.jpg
I am starting to get very concerned as I cannot get the ECU to give me any fault codes. I have disconnected the battery multiple times to try and reset it, also taking the ECU out the car for a couple hours to inspect it. But I still have the same problem. Starting to think the ECU is faulty?

Any help would be appreciated, as can't seem to find this issue anywhere online.

Thanks,

Gregor
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jimi
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Re: Check Engine Light - Fault Reading

Post by jimi »

Have you checked the initial conditions as detailed here ?https://www.mr2oc.co.uk/know-your-2/mk2 ... bartid=162
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Re: Check Engine Light - Fault Reading

Post by MR2DI4 »

Its been so long since I did a checklight test I cannot quite remember the correct sequence. After bridging the 2 points in the box do you you not first click the ignition switch to ACC and not turn it right on ?

Highly doubt its an ECU problem. Someone will post up the exact sequence from the Toyota BGB or its probably in the FAQ section already if you search.

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Gregor_99
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Re: Check Engine Light - Fault Reading

Post by Gregor_99 »

Hi,

I have been doing it as per the BGB instructions, down to the letter. However I do have an aftermarket imoboliser fitted, which I beleive cuts power to the ECU as EML light does not come one when the immobiliseer is active. But I make sure that the immobiliser is deativated when trying to get codes.

Thanks.

Edit: I also accidently broke the wire to the oil pressure switch whilst fitting a new temperature sensor, and the oil pressure light is not coming on, on the dash. Even when turing the key to the ON position, think the car has always had this problem.

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Re: Check Engine Light - Fault Reading

Post by MR2madlad »

Hi

Mine does the same as the original posters but is the slightly older 89661-17350, 1992 G-Limited.

Check engine light on constant, bridge E1 - TE1 engine light does not flash but remains on constant.

Unfortunately its IS a faulty ECU, I'm an electronics repair engineer and have spent several hours trying to fix.

I've got a used ECU from a 1993 same P/N 89661-17370 as your faulty one (hope this one lasts) and its cures the problem, car runs lovely now, idles a bit high thou so will check or fit the newer rev 3 TPS to it if needs be.

I replaced the capacitors in my original faulty ECU as 2 had leaked with Nichicon and Panasonic 105 Deg C all same value as originals, this did NOT rectify the issue but a heat gun does temporarily fix it.

Warming up the smaller PCB (not the larger one with connectors on it) under front cover with heat gun for 20-30 seconds from 4 - 5 inches away and the faulty ECU works, do it with engine running your hear it change / engine run nice, enters diagnostic mode fine, light flashes away to indicate no fault codes, leave it to cool down faulty reappears.

From my fault finding it looks likely the main control IC is defective its marked IC501 as its very sensitive to heat around / on it, so I highly suspect this chip is essentially Donald Ducked = new ECU

The enter diag sequence is normal link E1-TE1, turn ignition to 2nd click then normally CEL light should flash (or be on constant if faulty ECU) if its not on, car is immobilised (press the button you normally press on alarm keyfob if the car has immobilised which will then allow car to start, or lock and unlock with alarm fob) there is no fancy sequence it is literally link the points and turn key to 2.

Also point out that swapping the faulty ECU to my turbo fault followed, its not a turbo ECU but 89661-17350 3S-GE it WILL start and run / idle on a 1994 turbo (obviously not run properly but good enough to test / verify a fault) so was good to prove the fault initially to the ECU, I didn't swap the turbo ECU to the N/A as I didn't unbolt it from boot.

So there we have it, faulty ECUs do happen on these cars, 2 I know of this year, yours and mine !

John
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Re: Check Engine Light - Fault Reading

Post by jimi »

Leaking/bad capacitors are showing up much more often on MK2's these days, similar problems are pretty rare on MK1's and I haven't come across any on MK3's .... Yet !
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Gregor_99
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Re: Check Engine Light - Fault Reading

Post by Gregor_99 »

Hi All,

Thanks for the replys.

As John (MR2madlad) had stated the ECU was indeed faulty. I managed to find another working ECU, Plugged it in and the car worked perfectly.

So, great find John.

Again, thanks for the replys. I hope this thread serves to help others with the same issue we have experienced.

Cheers,

Greg
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