DeZyn243

So I have looked around for different posts on my particular issue and I did not find any, so I apologize in advance if I am making u guys repeat urself.

Let me give u guys a thorough understanding of what I have done and where I am at now with diagnosing.
My problem first started with the fact that my car was idling in a parking lot after I drove maybe 2 miles or so from my house and as I was sitting there the car just turned off.
I tried to crank her up and it just wasn't happening. it wuld turn over and not start.
So I logged into Mitchell on demand and followed the diagnostic steps as ordered (fuses, fusible links, relays) and they all check out and are within specs.
The next step said to jump +B and FP at the diagnostic connector and that's when I noticed I was not getting any power to my DLC.
I tested my Engine & ECT ECU according to Mitchell "ECU Power Source Circuit" diagnostic steps (pics of Mitchell required diagnostic steps below.) and step 1 said to back probe +B, +B1 and E1. They both read 1.3v even tho Mitchell said it shuld read batt voltage.
I continued on to step 2 and I have a closed circuit.
Step 3 read batt volt as required.
Checking the wiring harness between the ECU connector and EFI main relay is something I don't know how to do so I went to step 7 got a reading of 59.5 but batt voltage is what is required.
The next step said to replace Engine & ECT & ECU so I did and tested that one and I got similar readings as my original ECU and my car still does not start.

Which brings me to my question of are both ECU's bad or am I missing something here?
I am now out of my range of knowledge as far as testing ECU's and getting it to allow me to jumper the DLC so I can get my car running.

All help is greatly appreciated.
Sorry for the long post.

RA40

iTrader: (6)

This is the check that Yamae suggests for checking ripple from the ECU to determine if the ECU is damaged by leaking capacitors.

https://www.clublexus.com/forums/ls4...-by-yamae.html

DeZyn243

yea.
I came across this thread that u posted, but the problem is I can't get my car to start to run the ripple test, unless there is a way to do so without starting the car.

paulz67

iTrader: (1)

It sounds like something I went through with my once-project/now daily driver '94 LS:

When you turn the key on to attempt to start the car, do all the dashboard warning lights come on as one would normally see?

When I bought my car it wouldn't start--no CEL, no spark, no power to the fuel injection relay--trailered it home 120 miles and spent the next several months tinkering-- I took apart the ECU, and had a tech check all the caps--ESR readings were fine. I also tried a known good ECU from my '93 LS. No luck there, either.

To get it running (once there's power to the ECU, you'll have power to the fuel injection circuit), I first wired in a bypass circuit, which partially worked. The car actually started but lots of interior functions that one would have with the key on weren't working (climate control blower, alternator charging, to name a couple things). Also, the warning lights that would normally light up on start-up didn't come on. I went through the wiring harness again from the under-hood distribution panel into the car interior (pulled the LF wheel, inner fender and wire harness covering,checking for physical damage and electrical continuity). All checked out, but it led me to inside the car.

The answer in my case is that the wiring harness connector inside the car (attached to the inside fuse panel/power distribution point) was slightly corroded, so I didn't have a solid electrical connection. That particular harness sends power to the instrument cluster functions, alternator charging light (part of the alternator circuit, btw), the HVAC blower supply and the ECU. I sprayed DeOxit electrical contact cleaner/conditioner spray onto both sides of the multi-pin connector at the distribution/fuse panel, worked it in and out several times, then re-assembled. All good since--four months and 10k miles later.

Hope this helps.
Paul
'93 LS, '94 LS Anniversary edition

DeZyn243

Thks for the info on how to get out running.
I'm walking out the door now to pick up another ECU n see if that one will function properly.
Without that I'm stuck
If the new one works properly, I will follow the rest of ur post to get the car running.
Thks

DeZyn243

Question:
My 92 didn't have a trac system, but the ecu for sale came out of a 92 that does have a trac system.
Can I use that on mine?

dicer

I would say no. Maybe some one like Yamae will know for sure.
Later I will study my books and see what I can come up with about your problem.

DeZyn243

So I just got the 2nd ECU and tested it and it is still not in specs just like the original and the one I brought yesterday.
When I turn the key "on" all lights illuminate except for the check engine light.
Can someone tell me please, is it me or am I just batting zero here?
It sucks that I can't move forward until I resolve this ECU issue.

dicer

What are you checking on the ecu if engine is not running?

If they are all not correct then maybe the Mitchell stuff is wrong. And besides I would not be unplugging anything to check anything with power applied, you could be goofing something up. And if you use an ohm meter to check, in most cases its a 9v battery that you are using, and that's not good if the circuit is designed for 5 or less volts. I guess DLC is Data Link Connector? I have no power to mine either in gen 1, and to use a scan tool it has to get its power from the battery. I guess I jumped too fast on this one, the scan tool will not receive power at the connector. Not sure why.


In a no start deal, first thing you need to check is, is the fuel pump working? Next is it putting out pressure? Next is it getting a spark? There is a test for the igniter system on youtube just go there and search it, I have put it here on a post somewhere. It could be a crank or cam position sensor problem too. Sudden stop I would not suspect the ecu, but I would now because you could have damaged everyone that you have attempted to test.

DeZyn243

I'm not unplugging n e thing.
The battery cables and ECU are connected and plugged in.
I back probed the wiring harness of the ECU at +B n B1, E1 and MEL terminals.
Look at the attachment I just put up.

Without my ECU providing power to the proper components I'm limited with the testing I can do.
I may have lack of knowledge as to being able to check the fuel pump and getting the vehicle to put out fuel pressure without being able to jumper wire the DLC terminals.
The ECU powers the DLC
If I'm wrong let me know.

DeZyn243

And on all 3 ECU's (original and 2 newly purchased) I got these readings
(Steps are in pics)

Step 1: +B = 1.3V, +B1 = 1.3V
Step 2 = Closed circuit
Step 3: 11.24V
Step 6: Ok
Step 7: 58.8mV

dicer

https://www.clublexus.com/forums/ls4...e-driving.html

Okay for now forget the fixation on the ecu. Read my posts in this thread. I'll hit the books soon..

https://www.clublexus.com/forums/ls4...driving-6.html
Does it get fuel??????????
Does it get spark???????
Lets do these first ECU later.

Yamae

The ripple test can be done without starting the engine. Measure the ripple voltage at the key position "ON". The ECU starts to work almost fully at "ON".

But I would check the fuel pressure first in a case like yours before checking the ECU. It needs a pressure gauge and an adaptor though. An alternative is to use a starting fluid.

dicer

You didn't do step 8, I bet the problem is a relay.

If you don't have power a B terminal then apply battery plus 12 to the FP terminal to jump the fuel pump.
You likely have a relay problem. Fuel pump relay also there is a fuel pump resister, did you check all the relays in the box behind the battery? And how are the battery connections is it full charge?

Here is the manuals Matrix chart for a no combustion meaning the engine turns but not run.

1 ECU power source
2 Ignition signal circuit
3 Fuel system circuit
4 Ignition coil
5 Spark plug
6 Injector circuit
7 Compression
8 Cold start injector circuit
9 Rpm signal circuit
10 Engine mechanical
10.1 Valve timing
11 ECU

I would add all wiring and connectors in there, and notice they place the ECU pretty much last.
All the info of which relay does what is inside the fuse box cover. Also there are fuses under the dash up from the driver side kick panel, for the ecu.

With the sudden stoppage of the engine again first things to check are spark and fuel, timing belt. Make sure the fuses are ok and the relays, if all are good there has to be power to the ecu, less a wire is bad. Are any of those ECU's you got known working units? Check for spark, check fuel pump and pressure, and injector signal, if not there then attack them.
Rule out the ignitors in that test if there is no spark.

Yamae

Which relay do you mean?