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

[Tools R Us]

Well, a bit of progress... Had only about 10 min to look at it last night. I started it up and moved the wire bundle above and behind the valve cover - this sent a small spark or two and shut down the engine. ...

Common issue, there was a plastic harness clip/retainer that held the harness away from the EGR pipe. With age it disintegrates, allowing the harness to contact the hot pipe, resulting in a short. The metal clip mount should still be there, put a couple of zip-ties through the hole in it and around the harness to hold it away from the pipe. Does it still have the issue? If not, you have found the problem, but is advisable to add some protective wrap, restore the wires as needed. The most important part it holding it away from the pipe.

This is one of the first checks we do on new to us rigs. At this age almost all are affected, it's much easier to tie it back, than repair after it's burned.

 

[Jeff Elliott]

Thanks @Tools R Us ! I crawled out there in the dark and I think I found the clip you're referring to!

The wire bundle is laying on the EGR pipe and I can see signs of melting on the pipe itself. That combined with the spark I saw when I moved the bundle while it was running tells me it's likely a short in there for sure.

Here's the big question - and I follow instructions well but I'm a noob on this truck - how do I create enough room to work on that bundle without taking the whole intake, etc. off the truck? It looks like I'd have to take what appears to be a heater valve off to even have a chance of unwrapping, splicing, etc. Here's a couple of pics - if anyone could help me out by suggesting the minimum stuff to remove to have a decent shot at this I'd be grateful! If I need to pull a lot to get in there, I'm thinking I might as well just replace the whole harness?

 

[Jeff Elliott]

And, in searching, folks are saying that new harnesses are no longer available but I see them available online... is it that the latest models (e.g. 96 - 97) are available or are none available and I'd be in for a disappointment if I tried to order?

I emailed Onur but he said he's not taking any new Mud clients so... I gave it a shot!

 

[Malleus]

I wouldn't replace the entire engine harness for that much money when I could fix a wire or two. As to what you have to take off...that depends on what's broken. I'd advise you to plan on removing the air chamber, but not the intake. That'll give you access to the injectors and all the other wiring between the air chamber and intake manifold. Worst case, you'll have to splice a new section of wire or two into the harness behind the EGR piping.

Now's the time to clean the throttle body and air chamber while you're in there. That means three new gaskets. You might as well replace the vacuum lines (all 2.7 meters of them; get the longest and shortest lengths if you're buying OEM) and the number 1, 2 and 4 by-pass hoses. You can get number 3 anytime (it's the one that wants you to break off the nipple at the middle of the radiator upper tank). If they haven't been replaced already, add the heater hoses to the list (they'll never be as easy to get to). If you want to bypass the rear heater, now's the time to remove the two hoses and the tee and replace them with the single hose the desert models got (bypass-done).

 

[Tools R Us]

Depending on how much work it needs: For some have been able to get it by removing the EGR modulator and valve, others also remove the heater valve and the harness to firewall mount bolts.

 

[inkpot]

Part of that harness goes between intake runners and continues out past the bell housing connectors below the PHH and it goes out over the transmission. Plus all of the sensor connectors on the head for the ECU and dash gauges. Can certainly be replaced but it is tedious running all the right connectors to all the right locations.

 

[Jeff Elliott]

Thanks so much @Malleus and @Tools R Us - Sorry for the basic questions but...

I'm guessing #2 is the throttle body and that #3 must then be the air chamber? Not sure what #5 & #6 are but am guessing they'll need to come out to get access to the harness. I think #4 is the heater valve and that #8 is the heater hose?

On vacuum hoses, I'm assuming I can use these diagrams? Are all the lines the same ID or different?

I googled for the by-pass hoses but all I got was the rear heater by-pass info (which I'm thinking I don't need to do since it's a SoCal truck with no rust???). Any suggestions on where to find them on the truck are greatly appreciated!

Thanks agin and sorry for being a noob... Hopefully won't last long (will get an FSM on the way next week)!

 

[ppc]

You have the numbers correct, 5 is the EGR Modulator, 6 is the EGR valve, 8 is a heater hose that goes down to a metal pipe that goes to the PHH.

 

[Malleus]

Your vacuum routing diagram is on the underside of the hood

...or not. This is mine.

The older FSMs had a schematic with everything on it. The newer ones (like yours) are split so the technicians don't have to look at things that don't pertain to the problem they are charging you to repair. You'll have to become intimately familiar with the manual to use it well. Everything's there, just not where I'd like it to be.

 

[Malleus]

This is just the EGR system:

 

[Malleus]

Thanks so much @Malleus and @Tools R Us - Sorry for the basic questions but...

I'm guessing #2 is the throttle body and that #3 must then be the air chamber? Not sure what #5 & #6 are but am guessing they'll need to come out to get access to the harness. I think #4 is the heater valve and that #8 is the heater hose?

On vacuum hoses, I'm assuming I can use these diagrams? Are all the lines the same ID or different?

I googled for the by-pass hoses but all I got was the rear heater by-pass info (which I'm thinking I don't need to do since it's a SoCal truck with no rust???). Any suggestions on where to find them on the truck are greatly appreciated!

Thanks agin and sorry for being a noob... Hopefully won't last long (will get an FSM on the way next week)!

The bypass hoses are:
number 1 - into rear of throttle body
number 2 - out of front of throttle body to water piping
(both 1 & 2 are under the inlet; you can't see them until you remove the throttle body)
number 3 - water pipe (no. 1 hose) to radiator top tank
number 4 - from water piping (no. 2 bypass) to thermostat housing

I can't stress enough that if you pull the air chamber, and definitely if you pull the intake manifold, change the no. 1 bypass hose. I just went through this with my daughter's '94, which is in its freshman year at Tuscaloosa; the local dealership had it for two days to replace the that hose before they broke down and pulled the intake, which took them the better part of the third day. They lost money on that job.

FWIW, the main hoses are:
number 1 - top of the DS corner of the radiator to water pipe (no. 3 bypass)
number 2 - water pipe (no. 3 hose) to thermostat housing
number 3 - bottom of the PS corner of the radiator to water pipe (no. 2 hose)

 

[Malleus]

 

[Jeff Elliott]

Well, more progress but I'm stuck! ... Edit, found out I need the E7 torx to remove the EGR studs... will have to wait to get the air chamber off...

A couple of pics:

 

[Jeff Elliott]

Well, I found a problem for sure... It may not be the problem (the #4 misfire) but it's still a problem. When I finally get this ERG valve off I will be able to repair it I believe pretty easily with heat shrink butt splices. Here are the pics - It appears that a yellow wire has been shorting with two black wires with red stripes. Anyone have enough knowledge of the injector wiring to speculate on whether that's the root cause?

Thanks all!

 

[Red Merle]

Thanks so much @Malleus and @Tools R Us - Sorry for the basic questions but...

I'm guessing #2 is the throttle body and that #3 must then be the air chamber? Not sure what #5 & #6 are but am guessing they'll need to come out to get access to the harness. I think #4 is the heater valve and that #8 is the heater hose?

On vacuum hoses, I'm assuming I can use these diagrams? Are all the lines the same ID or different?

I googled for the by-pass hoses but all I got was the rear heater by-pass info (which I'm thinking I don't need to do since it's a SoCal truck with no rust???). Any suggestions on where to find them on the truck are greatly appreciated!

Thanks agin and sorry for being a noob... Hopefully won't last long (will get an FSM on the way next week)!

Those diagrams are for two different years. The top one is for a '93-'94 and the lower one is '95-'97. What year is your truck? Add the truck to your sig line so we can see what we are working with.

 

[Jeff Elliott]

Those diagrams are for two different years. The top one is for a '93-'94 and the lower one is '95-'97. What year is your truck? Add the truck to your sig line so we can see what we are working with.

Updated signature! It's a 97.

Would certainly love it if someone had a opinion on the likelihood that the burned wires are the source of my misfire / rough idle. I've got a couple of other questions but am holding them until this one gets some action

Thanks all, you're a life saver!

 

[Red Merle]

Updated signature! It's a 97.

Would certainly love it if someone had a opinion on the likelihood that the burned wires are the source of my misfire / rough idle. I've got a couple of other questions but am holding them until this one gets some action

Thanks all, you're a life saver!

The burned wires would be my first fix. That could easily cause the problem. If it persists, you'll have to keep going. Those wires look bad. You are on the right track with the splice idea though.

 

[Jeff Elliott]

Ok folks, the air chamber is off! I have 5 burned wires to fix which I can handle.

Here are the big questions that I could use some help with:

1) Beyond what Malleus suggested above in terms of replacing bypass hoses - what else should I replace "while I'm in there"?

• Vacuum Lines?
• Fuel Filter?
• PHH?
• Heater Valve?
• ???

2) Where can I buy this stuff?

• For what you suggest should be OEM, I tried Onur but he's not accepting orders / clients right now... anyone else?
• For non-OEM, are there other Mud sponsors I can support?

3) Should I pull the injectors (only 89K miles) and send 'em off?

Thanks yall!

 

[Tools R Us]

Most injection stuff, including injectors, are powered by the B/R circuit, #4 injector is ground trickered by a yellow wire.

 

[Red Merle]

Ok folks, the air chamber is off! I have 5 burned wires to fix which I can handle.

Here are the big questions that I could use some help with:

1) Beyond what Malleus suggested above in terms of replacing bypass hoses - what else should I replace "while I'm in there"?

• Vacuum Lines?
• Fuel Filter?
• PHH?
• Heater Valve?
• ???

2) Where can I buy this stuff?

• For what you suggest should be OEM, I tried Onur but he's not accepting orders / clients right now... anyone else?
• For non-OEM, are there other Mud sponsors I can support?

3) Should I pull the injectors (only 89K miles) and send 'em off?

Thanks yall!

Wit's End has some of that stuff.

Wits' End Solutions for 93-97 80 Series Land Cruisers

McGeorge isn't a Mud vendor but they have very good pricing on Toyota parts.

McGeorge Toyota Parts Online | Your Source for Genuine Toyota online parts | parts.mcgeorgetoyota.com

Otherwise, I always recommend developing a relationship with the parts people at your favorite local dealership. Mine will match McGeorge most of the time and I don't pay shipping and returns are free.