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Old 11-18-12, 02:59 PM   #1
bogeyjh
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Question 1994 LS400 will not start

I've been battling an non-starting issue with my 1994 Lexus LS 400 with no success to date. I'm at the end of my rope and considering taking it in to the dealer for service (ugh!), so I'm turning to the forum for suggestions.

The issue first presented when my wife was on an errand and called to say the car wouldn't continue to run after starting it and that the check engine light was on.

I went to rescue her and was able to get the car to start, but it would only run with higher RPMs. Even then, it wouldn't consistently run no matter what I did. I managed to get the car home, which was not far, but I must have restarted it a dozen times in less than a quarter mile to get there.

The next day, it wouldn't even restart. It would catch, indicating the coils were firing, but would die immediately.

Using the tutorial from LexLS.com, I read check engine trouble code 14, which indicates a problem with the Ignition No. 1 Signal Circuit (left/driver side). According to the service manual:
"No ignition confirmation signal 1 to ECM (Engine Control Module) for 8 - 11 consecutive Ignition 1 signals."

Possible causes I checked:
  • Igniter No. 1 - verified good including power source
  • Primary and Secondary Coil No. 1 - verified good including coil wire
  • Crankshaft sensor - verified good
  • Camshaft Sensor No. 1 - verified good
  • Engine Control Module - verified good (rebuilt last year and sent back for warranty service when this problem presented to eliminate ECM as a suspect)
  • I reset the ECM (sometimes referenced as ECU) by pulling the fuse, and verified the code was cleared (check engine light flashes ~4 times per second). All that is required to trip trouble code 14 again is to turn the ignition switch to the ON position without cranking the engine.

Any suggestions are welcome.

Last edited by bogeyjh; 11-20-12 at 08:10 AM.
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Old 11-20-12, 06:27 AM   #2
Dtwillis5
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You said the cel light on . See what codes you get. Sound like a fuel problem to me see If its getting gas
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Old 11-20-12, 06:49 AM   #3
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keep in mind that a common reason for unexplained starting issues on LS400 are bad ECU capacitors, a known defect on LS400

In any event, until it is fixed, use starting fluid to start engine, because the starter is very difficult and expensive to replace on an LS400 (very high labor hours) and so in order not to ruin it, never crank the starter more than about 5 seconds in an attempt to start (it will start within 5 seconds after a 1 second shot of starting fluid into the intake) - if it won't crank within 5 seconds, you need to let it rest at least 15 minutes between tries

Last edited by LScowboyLS; 11-20-12 at 07:55 AM.
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Old 11-20-12, 08:29 AM   #4
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Thanks for the input guys!

Thank you for the caution on the starter. I really would hate to exacerbate the issues with another and even more expensive problem.

The only code I get is 14 - no others.
I'm pretty certain the ECU is not the culprit. I had it rebuilt by ASI last fall and sent it back for a warranty service check as stated in the initial post.

Additional info:
  • It seems to catch when cranking (that point where you normally release the key), but will not run.
  • When I limped it home on day 1 it ran smoothly at higher RPMs, but died suddenly and often.
  • I'm pretty certain there isn't a fuel problem since when cranking I can smell gas (flooding due to no start). I would think that Is a safe assumption.
I had thoughts that maybe it jumped timing, but haven't gone there since it isn't likely.

I've also had thoughts that it may be the distributor. But since my coil test was a static test, swapping the coils will definitely precede action on the distributor since it is much simpler and might further eliminate or confirm the coil as the culprit.
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Old 11-20-12, 10:44 AM   #5
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check for open or short in IGF1 and IGT1 circuit from No. 1 igniter to ECU
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Old 11-20-12, 11:01 AM   #6
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Old 11-20-12, 02:19 PM   #7
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Thanks LScowboyLS.

It looks like I've done much of what is outlined there, but I didn't check for open or short in the harness or connector between the ECM and igniter.

Can you provide page IN-34 for that procedure? I'd rather not invent my own.

Last edited by bogeyjh; 11-26-12 at 07:25 AM.
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Old 11-20-12, 04:44 PM   #8
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Quote:
Can you provide page IN-34 for that procedure? I'd rather not invent my own.
here ya go

the procedure is really more on page IN-35, actually

Last edited by LScowboyLS; 11-20-12 at 05:03 PM.
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Old 11-20-12, 05:30 PM   #9
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Quote:
Originally Posted by bogeyjh View Post
I'm pretty certain the ECU is not the culprit. I had it rebuilt by ASI last fall and sent it back for a warranty service check as stated in the initial post.
Since your ECU was rebuilt last fall and you consider and believe it is not the problem since the fix was done at ASI. But judging from the symptoms and also from my experience, your ECU might have a new problem.

How was the ECU rebuilt?
Did they change all the Nichicon PF(M) capacitors?
Were low ESR capacitors used replacing all the Nichicon PF(M) capacitors?

I help shop owners to fix ECUs and sometimes I need to fix ECUs that are once fixed by a private company. Those were fixed using regular electrolytic caps that were not low ESR type by the company and failed again. Hearing from the owner of the car, I found that the car ran OK after the fix but it began to show a new problem in a year or so.

As I check those ECUs, I usually find caps that are not low ESR type or even some caps are not changed. Those caps that contain "quaternaty ammonium salt " should be all replaced as is written at the thread LScowboyLS indicates.

If your efforts so far do not fix the problem, I suggest you to see inside of the ECU and check what I wrote with question marks above.
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Old 12-10-12, 02:56 PM   #10
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I've been quite busy lately, so I haven't been back here to let you guys know the final fix for the LS400.

LScowboyLS,
No open/short issue was in the IGF1 and IGT1 circuit from No. 1 igniter to ECU

Yamae,
Back in November 2011, ASI repaired the ECM using low ESR capacitors for all the the original ammonium salt electrolytics.

When the ECM was returned for warranty service (November 2012), ASI fixed a problem they found in an area not related to the trouble code 14 (ignition circuit). After re-installing the ECM, I continued to have non-starting issues.

All troubleshooting led me right back to the ECM, thanks to some good input from several helpful souls on this board. The bottom line is that the ECM ignition circuit would function normally when disconnected from the load of the igniters, etc., but once it was reconnected, it could not drive the load. This condition was not detectable using the recommended diagnostics from the service manual, which test the ECM without the load of the igniter and incorrectly specified replacement of the igniter #1. Swapping the igniters proved that was an incorrect resolution. The problem was finally identified by using an oscilloscope and connecting a T-pin into the IGT1 signal at igniter #1 to identify the bad signal under load.

I returned the ECM to ASI with detailed info and they located an issue in the #1 ignition circuit, repaired it, and sent it back. They paid for shipping to and from since they had not fixed the described issue previously. I re-installed the ECM (again) and the ol' girl cranked right up.

Thanks again to you all for your valuable input, my wife is happy to have her car back up and running.

Last edited by bogeyjh; 12-10-12 at 03:07 PM.
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Old 12-10-12, 04:01 PM   #11
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call me a suspicious type, but this sounds like some sloppy work by ASI may have precipitated the starting problem in the first place

my money is on the theory that they basically fixed their initial screw-up after you sent it in for a 3rd? time

other than this capacitor issue, which is Nichicon's fault, NipponDenso ECU's just do not tend to have ANY issues!

but anyways, happy you have it running good! - yamae & I can smell an ECU issue a mile away!
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Old 12-07-15, 05:26 AM   #12
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I know this is an old thread and these cars are getting long in the tooth if they are even still going, but I wanted to add up update that may help someone since this thread gave me some direction.

1993 LS400 ran but the engine would die after about 20 minutes then it would crank but not start until the car cooled over 4-8+ hours depending on the temperature.

Pulled the ECU and found one capacitor leaking. Decided to go ahead a replace all electrolytic capacitors and there were a few more on the way out. But the capacitors did not resolve the problem. Exact same symptoms.

So pulled the ECU again and carefully inspected the circuit board very carefully with a bright LED flashlight and magnifier. Found on questionable resistor. The thing was it looked like some of the capacitor leakage, but there were no capacitors near by or on top of the resistor.

The resistor was hard to reach, but got a small stiff bristle brush and clean the silicon board sealer that had turned a bit brown off of the resistor and carefully inspected the resistor and solder joints for the resistor.

After a close inspection I decided to reflow the resistor because the solder joint on one side looked suspect.

I wish I would have take pictures or make a note of the resistor number, I recall it was 200 series resistor R2xx that appeared to be a lower value resistor that was right in line with the E9 ECU connector. This resistor was next to the 2nd larger transistor array that is a black vertically mounted component that is about 1 1/4" wide and about 3/16" thick.

Well luckily after reflowing the resistor solder joint I can say this solved the mysterious engine quitting after about 20 minutes. I think the problem was the resistor solder joint would warm up and loss the connection after about 20 minutes of run time.
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