Help, Trouble Code P1600 With Lots Of Greyish White Smoke, Unburnt Fue

[tsarang]

HELP, My baby is sick!!!!!!!!!!!!!!!!.

I was driving late at night and my 96 LS400 developed a check engine light, there was no power loss or any misfiring so i kept on driving as my home was near. I stopped at a signal and the check engine light started flickering with TRAC doing the same. Engine was revving like crazy with light white smoke which was light at first then it started to get pretty thick, I had to switch the car off and put my Hazard on. It was though I had blown off a gasket, piston or something.

I was close to home so I decided to take a chance and restart my car just to see what happens, this time it started with the check engine light on but no smoke. Eventually I limped home without any majour exhaust issues.

Next day i restarted the car, initially there was no smoke but then it started again, stuttering engine, raw fuel smell and lots of smoke. I looked at the the Trouble code, it was P1600, which pointed to an issue with ECU battery malfuntion,

looked up the Forum here http://us.lexusownersclub.com/forums/index...mode=linearplus

this gives a good idea to troubleshoot this code. its says to perfom the following test tp see if the ECU is bad

a. remove instrument undercover and measure voltage between terminal battery of ECM and body ground.

my question is how to do this?

where is this connection?, I mean the connector shown (see pic below), where is this at?

http://us.lexusownersclub.com/forums/uploa...65210_thumb.jpg

I was able to see the procedure to get at the Instrument panel here http://www.lexls.com/tutorials/electrical/...entcluster.html

and I see that there are three connectors, which one should i be using?, I am confused, Please Help.

b. I already tested the efi1 fuse connectivity with an ammeter, and checked the harness wire which seems to be fine visually (is there anything that can be done to verify connectivity more precisely here)?

any help will be greatly appreciated. Thanks Gurus!!!

[N.C.O.]

I don't think the P1600 has anything to do with you running problem, it has more to do with the power supply for the ECM's backup memory and its ability to store trouble codes.

Your original description with the blinking Check Engine Light would indicate that there is a misfiring condition that may resulted in damage of the catalytic converter. It is possible that you have either a bad coil or spark plug problem. The exhaust smoke that you are seeing, is it gray or white? White smoke would usually indicate a blown head gasket, and you would also experience coolant lost. Gray smoke on the other could be unburnt fuel going out the tail pipe.

Try to see if you can retrieve the codes with the engine running when the check engine light is on.

N.C.O.

[tsarang]

Hi N.C.O, Thanks for your reply.

I already tried to get a code from the ECU with the car started but keep on getting the same P1600 code. It wont give me any other code except the P1600.

The smoke is greyish/dark white and smells heavily of fuel. I don't think it is a blown head gasket because the car ran fine the second time it started without any smoke at all.

at this stage I am leaning at a bad ECU since a bad/dead ECU will cause the whole EFI system to crap out.

before following this expensive option I need to verify that the ECU is dead following the procedure listed in the manual. It states that you will need to remove the instrument cluster to get to a particular connector, I cannot figure out what this connector is?.

I was following the procedure in the manual to troubleshoot this. Please see the below links.

http://us.lexusownersclub.com/forums/index...ost&id=7265

http://us.lexusownersclub.com/forums/index...ost&id=7266

[killerFatty]

Gray smoke on the other could be unburnt fuel going out the tail pipe.

N.C.O.

My 93 puts out alot of gray smoke naustious smell when its cold. after a thurough warm up it goes away. Waht could be causeing that??

[tsarang]

Hi N.C.O, Thanks for your reply.

I already tried to get a code from the ECU with the car started but keep on getting the same P1600 code. It wont give me any other code except the P1600.

The smoke is greyish/dark white and smells heavily of fuel. I don't think it is a blown head gasket because the car ran fine the second time it started without any smoke at all.

at this stage I am leaning at a bad ECU since a bad/dead ECU will cause the whole EFI system to crap out.

before following this expensive option I need to verify that the ECU is dead following the procedure listed in the manual. It states that you will need to remove the instrument cluster to get to a particular connector, I cannot figure out what this connector is?.

I was following the procedure in the manual to troubleshoot this. Please see the below links.

http://us.lexusownersclub.com/forums/index...ost&id=7265

http://us.lexusownersclub.com/forums/index...ost&id=7266

Ok guys, i figured out how to remove the glove box and get at the ECU and the connectors. Tested the connector as advised there seems to be no voltage at all at the connector. i further went on to check the fuse and tried detecting a voltage and could not find any voltage coming there too!!!!. IS THE HARNESS FRIED?. how can i further test this?.

i wanted to point out that before this issue happened I had changed my motor mounts. i remember the mechanic had a hell of a time removing one of the mount and he had to jack the engine up like crazy. would that have caused damage to the harness?. Did anybody have this experience?

I opened the ECU too.. found all capacitors leaking, blank gunk on the circuit board. I want to further go ahead and clean this using electrical cleaner. let me know if it is OK? should i go ahead and replace the capacitors too?

After seen the gunk, How do I know the ECU is fine? is there a test I can perform to Verify 100%?. My OBCD reader connects to the ECU to get the P1600 code so can i presume ECU is good?. can i supply 12V directly to the ECU, By attaching a wire directly to the ECU?. In that case what should the voltage be?. 12V?

Gurus Kindly respond. Thanks.

Thanks for the Help Guys -- Tan.

[eatingupblacktop]

If your caps have leaked onto the board, then chances are that the protective film on the board to protect the circuits has been damaged. With the ECU unable to control the EFI, you're getting excessive fuel, a lot of which is coming out the exhaust as you can smell. Don't know if you can revive the board and get away with just replacing the caps. After repairing/replacing the ECU, I would check/clean a few things like the coils, O2 sensors, EFI relay, plugs, etc.

[landar]

I would have to agree with eatingup and say I dont know that you can revive your ECU at this point. Personally,

if the caps are shot, then I would get a new or used unit at the salvage yard. Would not mess with trying to "fix" it.

Now, the question in my mind is: why did the ECU caps blow in the first place? Did you ever have to replace the alternator/regulator

or battery recently?

Electrolytic capacitors typically are stressed and blow when an overvoltage or reverse voltage is applied.

Make sure that the alt/reg is putting out the correct voltage range(13-14.5V) AND is DC. You might have a failed rectifier in your Alt. which is

putting some AC on the line(although the battery will help to smooth it)

In any case, I would carefully check out the supply (ie: alt/reg/battery). Something is rotten in Denmark, er Florida <_<

[tsarang]

Thanks for your excellent feedback eatingupblacktop and landar.

I had a suspicion that the ECU is bad but today its confirmed. I had a doubt that the harness can be the issue as a result of the Engine Mount's change. but I

finally found out that I was testing the voltage to the ECU incorrectly at the wrong connector.

http://us.lexusownersclub.com/forums/index...ost&id=7266

the battery terminal "BATT" has to be accessed from behind the connector. It is the first slot as shown in figure.

I was incorrectly testing from the opposite side, being a mirror image the connector slot was wrong and I was getting no voltage at all. I got 12V proper at the

right BATT terminal, just to be 100% sure I was testing the right connector I went ahead and disconnected the EFI no 1 Fuse, This broke the connection,

so it is confirmed that there is an issue with the ECM and not the Harness.

you guys are right we also need to find what would cause the ecu to fail. The Capacitor leakage can be due to capacitor issues with older capacitors,

Capacitors buid before 1999 have a tendency to leak after they get old, ~10years. The electrolyte is caustic and causes short circuits frying ICS .

another possibility as pointed out by Landar is Bad Voltages which can also cause major damage. Yes I did have the alternator fail and replaced the alternator

with a rebuit part. I will remove it an get it tested again just in case.

I have found a replacement ECU for about 100$ from a Salvageyard and gone ahead and ordered it. My only concern is that my Key will not work. also my car

is equipped with traction control, will it support that Logic?. I will be lucky if it will be 100% fit. but otherwise what option do I have? can the original

programming transfer from my old ecu to the new one? I also spoke with people who fix ECU's, he said possible for $250

will this be a good approach? any body done this?, any issues later? THANKS.

[tsarang]

Guys/ Gurus any Idea's/Feedback. Your Help and Input is greatly appreciated. Thanks.