FIXED!!! Bad ECU - Runs rough, CEL and P0304 (1 Viewer)

[jfz80]

Jeff. Thought i had replied, but yes those wires could definately be the source of your issue And if not, the beginnings of a new one.

1) yes
All those are good to tackle. Also cautiosly clean out or bypass the pass through pipe in upper half of intake. Replacing VSV for PM would be extreme but you would have good access. Get the vaccum line in bulk and cut to fit.
2) I know your kinda far from clt but scott clark offers ONSC guys a discount. A couple folks have had better luck with town n country i believe and also gotten fair prices. Fred Anderson in rdu offers a discount as well but then you have shipping. There are a few online sites i cannot recall and havent used but seems folks are happy with.
3) i probably wouldnt but will only cost you a week and ~150 bucks. Witchunter is one service group.

 

[Jeff Elliott]

Thanks all!!!

I checked the impedance on the #4 and #5 injector and both registered 16 ohms so I'm thinking the injector is good. Based on this, I'm not going deeper on the injector front and working under the assumption that it's the wiring that's the issue.

In addition, I've ordered about $200 worth of maintenance parts (damn) including all the vacuum lines, bypass hoses, throttle body and air chamber gaskets, valve cover gasket, tube gaskets, PCV, gaskets, etc.

Going to hold off on the heater valve right now but will replace when things are running right (fingers crossed) and post flush of the cooling system.

Somebody redirect me if I'm missing something - otherwise I'm going forward!!!

Thanks,
Jeff

 

[Jeff Elliott]

Ok folks, back making progress after a vaca with the family all week. Stuck again.

I ordered all the OEM rubber lines listed by Beno in this thread Silicone Vacuum Hose / Line Sizes? I'm replacing everything now but have some lines that I just don't know where they go (and Google isn't providing any diagrams that help me identify). Here's a pic of what's left to be installed - any chance anyone can point me in the right direction?

 

[Jeff Elliott]

Well folks, though I still need some help identifying where the above hoses go, I have it all back together and running. However, it runs identically to how it ran before I made the wiring repair.

In the meantime, I bought a mechanics stethoscope. After I got it running I checked the other injectors and i can hear them ticking. However, #4 doesn't tick. I had previously tested the resistance of this injector against others and it measured identically. Given it's not "ticking" and the rough running continues, I'm assuming my next step is to pull the throttle body, air chamber, etc. and remove all the injectors and send them off? I hate to but, unless you have a better idea, this seems necessary.

If that's what's next, does anyone have a recommendation on where to send them and any idea of the typical turnaround time? I have serious WAF issues given the rig is sitting in the garage in pieces and need to get it back on the road and out of the garage asap!

Thanks to all!

 

[inkpot]

Have you put a meter on the #4 injector socket to see if it gets a trigger signal?

 

[Jeff Elliott]

Have you put a meter on the #4 injector socket to see if it gets a trigger signal?

Thanks @inkpot - I was going to do it at the ECU because #4 is a PITA to get to with everything assembled. I could barely get the stethoscope in there to verify that it wasn't ticking. If you can think of a better way to do it at the injector, I'm all ears!

Otherwise, I was going to try the procedure I found in another thread do check it at the ECU and see what happens... Here's what I found:

One side of the injector is fed from IGN switched +12V. That +12V goes to all 6 injectors. The other side of each injector goes back to the ECM (which pulses each side to ground to activate the injector).

It appears (from the 1996 EWD) that you could connect the meter (on ohms) to the 7.5A IGN fuse (which would be the ignition switched +12V feed to each injector in the harness) and the other side of the meter to the ECM harness pin of each injector -ve connection. You should see around 13 ohms for each reading which is the correct resistance for a good injector (if the wiring is intact). This all done with the key out of the ignition obviously.

You have to measure one injector at a time. Each should be around 13 ohms. The above assumes the '93 wiring to the injectors follows a similar scheme as the '96.
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It looks like this route will only confirm what I found when I checked the resistance at the injector as well as that I'm getting +12V. I don't know how to check it specifically for signal - any adivce?

Thanks again!!!

 

[Tools R Us]

...
It looks like this route will only confirm what I found when I checked the resistance at the injector as well as that I'm getting +12V. I don't know how to check it specifically for signal - any adivce?

Thanks again!!!

Check the resistance on the wires at the ECU, with the connector unplugged from the ECU. Should be very close to the result you got at the injector.

 

[PDoyle]

hmmmm, what about the wiring behind the glovebox next to the firewall?
i need a fish emoji here ( ) .

 

[tampacruiser95]

I am shocked by this given the lack of rust and history.

 

[Red Merle]

Just warning you that a '93-'94 wiring diagram is not going to be the same as a '96. Totally different wiring. '93 didn't have OBDII and there was a bunch of changes to the wiring due to no airbags, PAIR, a different oil pan, different transmission wires, etc. They should almost be their own class of LC, but they are part of the evolution and knowing which one you have makes a huge difference. I have the full EWD for the '94, but it wouldn't serve you to have that. You need the '96. You can download all of it off the Toyota website for a few bucks.

 

[Jeff Elliott]

Just warning you that a '93-'94 wiring diagram is not going to be the same as a '96. Totally different wiring.

Thanks Red Merle - I downloaded the '96 version here on Mud that Trollhole posted. Here's what I'm using - specifically #40 below.

 

[Jeff Elliott]

Update #2 - Calling @Tools R Us , @jfz80 , & @Malleus

I need some help figuring out how to test for resistance at the ECU - The way I read the diagram above, to test across the injector at the ECU I should look at the resistance between the first and second wire listed per cylinder. For example, to test #1, I would connect my leads across E4-12 and E4-13. I'm not getting anything on any injector so I'm obviously doing something wrong.

That said, here's what I was able to find:

• I have ignition on cylinder #4 - verified with timing light
• This is very weird - All my "IG switch ON" wires for all injectors EXCEPT #4 show 12.6V... #4 shows 11.83V I verified several times and without moving my ground

Thanks to all... I'm trying not to give up on this f$#%ing expensive and non-running purchase!

 

[Tools R Us]

To measure resistance you have to use the gauge fuse and the injector, but the voltage check will work fine. The voltage being low indicates a bad connection or bad injector. But you confirmed injector resistance was consistent so volt test should be the same for all of them, indicating connection problem.

Hook the meter up, place where you can see it. Move/flex the harness pigtail for #4 injector, watch the meter, does the reading change? We have seen broken wires at the connector, but most often where the pigtail comes out of the main harness.

 

[Jeff Elliott]

To measure resistance you have to use the gauge fuse and the injector, but the voltage check will work fine.

Thanks! Is the gauge fuse connected to a pin in the ECU harness or do I need to find it in a panel? If so, anyone know what it's called in the pinout diagram? If not, is that fuse under the hood or in the cab?

Hook the meter up, place where you can see it. Move/flex the harness pigtail for #4 injector, watch the meter, does the reading change? We have seen broken wires at the connector, but most often where the pigtail comes out of the main harness.

Will do - do you mean to do so looking for a change in the voltage or change in the resistance (assuming I can figure out how to measure that at the ECU!)

 

[Tools R Us]

Thanks! Is the gauge fuse connected to a pin in the ECU harness or do I need to find it in a panel? If so, anyone know what it's called in the pinout diagram? If not, is that fuse under the hood or in the cab?

In the cab box, key needs to be to run, but the volt reading that you are doing will work fine.

Will do - do you mean to do so looking for a change in the voltage or change in the resistance (assuming I can figure out how to measure that at the ECU!)

Either will work, should not have a change in value when wires are moved, if there is, you have found the problem spot.

 

[Jeff Elliott]

Thanks @Tools R Us!

I was inspired by the awesome 80's I saw at my local club meet (long time listener, first time visitor - thanks @JohnVee !). I came home and spent a couple of hours with the rig and here's what I can report:

• Pulled throttle body so I could get to #4 injector. Unplugged and tested resistance - 14 ohms. Pulled #3 and it measured identically
• Tested resistance for all injectors using the method Kevin described above. All injectors including #4 measured the same at the ECU
• Reassembled everything and took it for a short drive (sans hood I might add). Within 30 seconds of pulling out of the driveway it threw another P0304

Given #4 tested good from a resistance perspective but low from a voltage perspective, combined with the fact that I couldn't hear it "tick" with the stethoscope, I'm going to assume that the # 4 injector is no bueno. If anyone disagrees (or wants to agree as that would be encouraging!), please do so asap.

Now, "since I'm in there"... It's only going to cost ~$10 more to buy remanufactured injectors from rockauto than to have my injectors flow tested. Would you replace them all with the remans or send the rest off?

Thanks to all!

 

[Tools R Us]

If you have a broken wire, it can and is likely to be intermittent. Most likely to fail with movement, vibration. Did you try moving, wiggling the wire to #4 with the meter connected?

 

[Jeff Elliott]

If you have a broken wire, it can and is likely to be intermittent. Most likely to fail with movement, vibration. Did you try moving, wiggling the wire to #4 with the meter connected?

Yup, moved it when testing voltage. I still have the ECU down so I will do the same again with resistance this time tomorrow and report back. For clarity, I wiggled 1) at the ECU connector, 2) as far as I could follow the wire bundle up inside the dash, 3) where the bundle exits the firewall, 4) where the bundle turns down beside the ECU connector and 5) and the #4 injector. Nothing changed voltage wise but we'll try with resistance for a "belt and suspenders" test.

Assuming resistance says the same (no wire break), would you replace the injector and, if so, would you do all or just one? Has anyone ever heard of a bad injector with a good continuity test?

Thanks!

 

[SteamerF18]

FWIW my '97 is at the tail end of a HG repair and a lot of WYIT's, one of those being the injectors. My Cruiser whisperer/ guru/ sensei/ resurrector sent the injectors off to be rebuilt and two were operating at about 82% efficiency.

Your rig and my rig are the same age, so are the injectors. Over to you, your budget and time, but if I was rebuilding or replacing one, I'd do them all to eliminate a similar issue down the line.

 

[Tools R Us]

... Has anyone ever heard of a bad injector with a good continuity test? ...

Would be very rare, most common would be clogged, but it would click. If you want to confirm, swap #4 with one of the others, if the code moves with it, it's the injector, doesn't it's wiring.