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Old 05-01-2016, 03:30 AM   #1
Join Date: Jul 2015
Location: Dallas, TX
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A.BuckShort is on a distinguished road
Question 93-94 Toyota Supra (or 93-94 Lexus SC300) WIRE HARNESS --or just harness connectors

If your time is limited, details and bottom line questions are at end of all this below.

OK. For those forum frequenters (Phil in particular) who may have been following our, now 10 month, battle to get an electrical signal to our unresponsive 1993 Supra 2JZGE [6 cylinder, automatic, non-turbo, federal emissions] fuel pump– this is what it’s come down to. (If it were a vintage German car instead of Japanese, we might tastelessly, but not unreasonably, label the quest “Mein Kampf." Have been allowed vehicular visitation rights on weekends, but mechanic alone has spent so much time with it, in West Virginia this would qualify as a common law marriage.)

Tried replacing fuel pump, then smaller fuel-pump-dedicated computer, then several replacement or rebuilt ecus (main computer under passenger’s side dashboard) with same Toyota OM # or from said-to-be interchangeable 93-94 Lexus SC300. Also tried separate ignition-to-fuel pump, fused, dedicated 12 v. wire, which should have worked, but didn’t – at least for us. So nada in one way or another.

With two of the ecus, our fuel pump started fine then soon cut back off. Noticed this always happened IMMEDIATELY whenever/if mechanic jiggled large bundle of wires in the wire harness up front. Etiology now evolved to being a shorted wire issue. Spent a lot of time fruitlessly trying to isolate the culprit in that Gordian knot.

With the original ecu installed, modified the “jiggle test” and detected a loose connection between one or both of the wire harness connectors and their 3 corresponding sets of pins (male ends) coming out of the side of the ecu. Sure enough, pump operated consistently when mechanic pressed and held the connectors into the pins; then cut off when he released the pressure. (Pin inspection showed all pins themselves looking factory perfect with no disfigurement.)

Then noticed a screw securing the harness connector to corresponding hole on the ecu (pin) side seemed a little longer than it should have been, thereby possibly preventing the two sides from being tightened to their fullest. (May have been introduced several years ago when dealership said it had removed the ecu for repair? Although ecu seal had not been broken, suggesting no work had actually been done on the ecu itself.) My mechanic added a washer that seemed to compensate for the screw length.

Still only connected when manually pressed together. Mechanic attempted to secure the two sides with a good number of plastic ties in different directions. Ran for quite a few minutes, then cut off as before. Since pins seemed ok, and connection seemed tight, etiology-of-record evolved to some problem in one of the harness’ two wire connectors.

MOST LIKELY SOLUTION : replace with a new or salvaged engine wire harness. Several complications:
1) New (i.e. aftermarket manufactured) 1993 Supra wiring harnesses listed on eBay $1,200-$1,600.
2) Even those listed were only for Supra GTE, not my GE – and we know from our experience, at least the ecus had to be same OM# from 93-94 GE, automatic, naturally aspirated, federal emissions – no other combination interchangeable. Assume same for the harnesses?
3) Or do you know if the GE and GTE Supra engine harnesses should, in fact, be interchangeable?
4) Saw no “pre-owned”/salvaged harnesses listed whatsoever; and even if found, could you trust one?
5) Putting in an entire replacement harness is somewhat formidable – involving having to tear apart a lot of the car to connect with all the different sensors.

MECHANIC’S WORKAROUND HACK FOR PROBLEM 4 ABOVE: Don’t need to replace the entire engine wire harness. Only need 1 or both replacement CONNECTORS to the ecu from a salvaged compatible harness. Snip off the replacement harness connectors with enough lengths of hanging wires to splice into the wires or the existing wire harness sections left in place.

1. 93 Supra JZGE parts seem to be scarce as chabo teeth (Japanese bantam hens if you must know).
2. However, salvaged wire harness from a 6 CYLINDER (not 8-cylinder) 93 or 94 Lexus SC300 should do the trick (as matching the automatic, nonturbo, emissions). So far, mechanic has only been able to locate salvaged harness from the Lexus SC400, which is 8 cylinder and does not match. Insists only SC300 6 cylinder will work.

1) Does the snip and reattach connector idea fly with you guys?
2) Any leads on 93-94 Supra GE (auto, nonturbo, federal emissions) or 93-94 Lexus SC300 affordable engine wire harnesses --or harness connectors alone, or anybody with salvaged vehicle willing to allow “snip and save.”
3) If it’s the only option found, should the harnesses from ANY model Supra be interchangeable, even if the ecus would not be?

Thanks, and especially for your tolerance.
A.BuckShort is offline   Reply With Quote

93-94 lexus sc300, 93-94 supra, wire harness

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