KZJ78 limp mode (1 Viewer)

[Black94Prado]

Here's another one for you

Another day another issue with the wonderful kzj78. So the truck is essentially in limp mode right now, it seems to pull relatively normal up to 2200rpm and then just stops at 2200rpm. This is true in Low, 2, D with O/D on or off, doesn't matter. Still feels like it has torque but a bit slow to respond to the pedal from a stop start, then turbo spools and she moves. No CEL. This started maybe a few days back in Belize. I'm in Guatemala now so getting a scan tool is a bit tough where I am. Uh what else... up to 95% throttle it will just stick at 2200rpm and maybe creep up a bit if going down hill, if I push it as hard as I can that last 5% it will downshift up to like 3100rpm. But if it's in Low or Second (especially going up hill) it will simply not rev up. In park and neutral it revs fine, turbo seems to spool just fine too.

Fuel filter is new, throttle cable adjusted, checked all the wiring and plugs, oil filter new, oil new, coolant is fresh and bypassing both heater cores, trans seems to shift fine and fluid is relatively fresh, EGR is deleted. EGT's are low and consistent with driving at 2200rpm or lower.

I also unplugged the batteries for a while and let the computer reset but no difference

 

[Tigris]

My guesses are either MAP sensor is sending a false value, or you ECU has gone bad.

Sorry to hear this and best of luck.

 

[Black94Prado]

My guesses are either MAP sensor is sending a false value, or you ECU has gone bad.

Sorry to hear this and best of luck.

Yeah map sensor is actually new as I broke mine off when changing the intake manifold gaskets. Figuring the ECU might be getting close.... Funny i was just reading your thread on replacing the capacitors

 

[Tigris]

Yeah map sensor is actually new as I broke mine off when changing the intake manifold gaskets. Figuring the ECU might be getting close.... Funny i was just reading your thread on replacing the capacitors

The ECU being on it's last leg is certainly a possibility, after all, one of the most common limp mode triggers is boost reading (or perception of) higher than 15psi, and since the ECU is the one in charge of activating the limp mode it makes sense that it might be going rouge.

Replacement of capacitors is recommended regardless of symptoms as the capacitors used in the ECU are among the batches effected by the great capacitor plague anyway.

Open up the ECU and take a peak. It takes a few minutes to do so.

 

[Black94Prado]

The ECU being on it's last leg is certainly a possibility, after all, one of the most common limp mode triggers is boost reading (or perception of) higher than 15psi, and since the ECU is the one in charge of activating the limp mode it makes sense that it might be going rouge.

Replacement of capacitors is recommended regardless of symptoms as the capacitors used in the ECU are among the batches effected by the great capacitor plague anyway.

Open up the ECU and take a peak. It takes a few minutes to do so.

Well spent the last 3 hours in a 4x4 shop here (super cool, they're building a few new 79 series and 80s plus hilux's). Anyways they were all super good guys and called like 10 different specialists, got some electrical guys to come over. We took the computer out and honestly it was the cleanest looking component in the whole truck. No leaks at all visible. So yeah might still be that but after going on 4 test drives with 3 different people they're going to pull apart the injection system tomorrow. Considering I went through a few fuel filters after picking up some seriously contaminated fuel in Mexico (including 2 Racor primary filters) we're hoping something is just plugging up the pump or injectors somewhere. Nice thing about Guatemala is they said it'll be about $80 for 6-8 of work lol. Fingers crossed.

 

[misterclean]

The caps on the ECU may have gone bad or are on their way out, causing the gremlin of an issue. If you have an electronics shop nearby that can test the caps and cross check their values, that may be your best bet. A few bucks and some new capacitors will at least be some solid peace of mind for the future!

 

[GTSSportCoupe]

The ECU will store codes even without turning on the CEL. Did you pull the codes?

Make sure there is no leak on the hose to the boost sensor. Sometimes they can pop off also.

Here's some good reading for you and the techs:

 

[GTSSportCoupe]

There's this too of course. Assuming you have it already, but if not...

 

[Black94Prado]

Hey thanks man yeah I had that last manual but the injection pump one is great, so anyways long story short these mechanics bounced me around shops for a bit but no one could figure it out or find an OBD-1 scanner but also didn't charge me anything. I've been in Antigua for a few days just letting the truck sit and met up with some other landcruiser people who helped me poke around and we used the paperclip method to flash the code using the CEL, which honestly worked great and I can't believe it.

Question is, it's throwing code 32. Few toyota sources I'm finding say it's: 32 - Air flow meter signal ----- and a few other sources I found for this truck say 32 is Correction resistor signal

Can someone confirm? We cleaned the MAF sensor just in case and the little air filter was indeed pretty gunked so we bypassed it to see if it helps but can't drive the truck until tomorrow it's in camper mode.

 

[FJ40 that green thing]

Im gonna take a wild guess that you are "Alone on Adventure" on youtube? Missing your content! This odd behavior that is unexplained sounds a lot like ECU which a replacement is pretty much unobtanium, rebuilding is about your only option. I am unable to confirm this is for sure your issue but it sure sounds like it. Even if the ECU looks ok, bad caps with minor leaking can short out traces that will effect various things regarding engine management. You are lucky it still drives at least. I am the one that asked if you had it rebuilt before leaving for SA. Balzy move! I hope you get it sorted out before too long.

 

[Rigster]

I found this on a prado site in AU:

Despite the 1kz-te being an old school technology engine its engine management is relatively sophisticated (It can be thought of as single point electronic fuel injection)

The codes stored in the ECU can be easily extracted at home and are displayed via the engine check light on the instrument cluster.

The codes can be read by shorting out pin 4 and 13 on the (16 pin) DLC3 connector located under the fuse box on the driver’s side of the dash.

A short piece of wire can be used to short the pins (tin the ends with solder and keep it in your tool kit)

Steps:

1) Make sure the ignition is OFF, throttle closed, Aircon OFF and if it’s automatic have it in P.
2) Turn the ignition ON but don’t crank or start the engine.


3) Put the jumper wire across the connector pins. (pin 4 and pin 13)
4) Read codes displayed via the engine check light.
5) Disconnect the wire when finished extracting codes and turn the ignition off.

Reading Codes:

Codes are read by the flashing of the “Check Engine” light on the instrument cluster.

If there are no codes held in the ECU then the light will have a continuous flash, on for ¼ second, off for ¼ second.

All the codes are two digit numbers. The first flash is 4.5 seconds from when you short the pins. It stays on for ½ a second then off for ½ a second. Then the first digit of the code will flash, followed by a 1.5 second pause then the second digit will flash.

Example:

4x flashes…. 1.5 second pause…2x flashes. Would be code 42.


If there is only one code the there will be a 4.5 second pause before the code will be repeated.



If more codes are present the codes the pause between codes will be 2.5 seconds.

To clear the codes from the memory of the ECU remove the fuse labeled “ECD” from the fuse box in the engine bay. Leave it out for 60 seconds.


(Don’t clear the memory by removing the battery or you will have to reset the clock, radio and windows)


Codes and what sensor/circuit it relates too:

1KZ-TE diagnostic codes:

12 = No RPM signal during cranking.
13 = No RPM signal after cranking and engine reaches 680rpm+
14 = Timing control signal (crankshaft angle 7 deg or more out from target)
15 = Throttle control motor (no signal)
16 = Auto trans control signal
18 = Spill control valve (no signal)
19 = Accel pedal position sensor (no signal)
22 = Coolant temp sensor
24 = Intake air temp sensor.
32 = Correction resistor signal.
33 = Intake constrictor control signal.
35 = Boost pressure sensor.
39 = Fuel temp sensor.
41 = Throttle position sensor.
42 = Vehicle speed sensor.
43 = Starter signal to ECU.
51 = Switch control system
96 = EGR valve lift sensor.
99 = Engine immobilizer.

The fault code 32 is a correction resistor short on the fuel pump. There are 2 of these resistors easily accessible on the side of the injection pump. I suspect one of them that perhaps looks after the fuel supply at higher RPM's is faulty in the harness or connector.

Now look into the KZ-TE manual above that @GTSSportCoupe so lovingly provided (page DI-32) and I suspect you will find the culprit. I hope you do not have to do all this from a cell phone screen. Sounds like it will be a quick fix as they refer to checking the plugs, harness, connections, etc. Good luck!

 

[GTSSportCoupe]

I found this on a prado site in AU:

Despite the 1kz-te being an old school technology engine its engine management is relatively sophisticated (It can be thought of as single point electronic fuel injection)

The codes stored in the ECU can be easily extracted at home and are displayed via the engine check light on the instrument cluster.

The codes can be read by shorting out pin 4 and 13 on the (16 pin) DLC3 connector located under the fuse box on the driver’s side of the dash.

A short piece of wire can be used to short the pins (tin the ends with solder and keep it in your tool kit)

Steps:

1) Make sure the ignition is OFF, throttle closed, Aircon OFF and if it’s automatic have it in P.
2) Turn the ignition ON but don’t crank or start the engine.


3) Put the jumper wire across the connector pins. (pin 4 and pin 13)
4) Read codes displayed via the engine check light.
5) Disconnect the wire when finished extracting codes and turn the ignition off.

Reading Codes:

Codes are read by the flashing of the “Check Engine” light on the instrument cluster.

If there are no codes held in the ECU then the light will have a continuous flash, on for ¼ second, off for ¼ second.

All the codes are two digit numbers. The first flash is 4.5 seconds from when you short the pins. It stays on for ½ a second then off for ½ a second. Then the first digit of the code will flash, followed by a 1.5 second pause then the second digit will flash.

Example:

4x flashes…. 1.5 second pause…2x flashes. Would be code 42.


If there is only one code the there will be a 4.5 second pause before the code will be repeated.



If more codes are present the codes the pause between codes will be 2.5 seconds.

To clear the codes from the memory of the ECU remove the fuse labeled “ECD” from the fuse box in the engine bay. Leave it out for 60 seconds.


(Don’t clear the memory by removing the battery or you will have to reset the clock, radio and windows)


Codes and what sensor/circuit it relates too:

1KZ-TE diagnostic codes:

12 = No RPM signal during cranking.
13 = No RPM signal after cranking and engine reaches 680rpm+
14 = Timing control signal (crankshaft angle 7 deg or more out from target)
15 = Throttle control motor (no signal)
16 = Auto trans control signal
18 = Spill control valve (no signal)
19 = Accel pedal position sensor (no signal)
22 = Coolant temp sensor
24 = Intake air temp sensor.
32 = Correction resistor signal.
33 = Intake constrictor control signal.
35 = Boost pressure sensor.
39 = Fuel temp sensor.
41 = Throttle position sensor.
42 = Vehicle speed sensor.
43 = Starter signal to ECU.
51 = Switch control system
96 = EGR valve lift sensor.
99 = Engine immobilizer.

The fault code 32 is a correction resistor short on the fuel pump. There are 2 of these resistors easily accessible on the side of the injection pump. I suspect one of them that perhaps looks after the fuel supply at higher RPM's is faulty in the harness or connector.

Now look into the KZ-TE manual above that @GTSSportCoupe so lovingly provided (page DI-32) and I suspect you will find the culprit. I hope you do not have to do all this from a cell phone screen. Sounds like it will be a quick fix as they refer to checking the plugs, harness, connections, etc. Good luck!

That's hilarious, I was just about to paste exactly the same thing, lol!

So further to that, I'd recommend OP check to see if the resistor connectors on the side of the injection pump are dirty or damaged. Maybe clean them with compressed air and contacts with an electrical cleaner and see if it makes a difference.

I replaced mine with multi-turn potentiometers in the cabin....and use them to fine tune my motor. (around 2.5k Ohm if I remember correct)

 

[Rigster]

That's hilarious, I was just about to paste exactly the same thing, lol!

So further to that, I'd recommend OP check to see if the resistor connectors on the side of the injection pump are dirty or damaged. Maybe clean them with compressed air and contacts with an electrical cleaner and see if it makes a difference.

I replaced mine with multi-turn potentiometers in the cabin....and use them to fine tune my motor. (around 2.5k Ohm if I remember correct)

Great minds think alike??

OR it could be the other side of the coin.... fools seldom differ...

I'm going to take an edumedicated guess and suggest it is the former!!

 

[Black94Prado]

Hey thanks guys for all the helpful info, yeah I am alone on adventure on YouTube.

Since I posted that I did go ahead and try some things running with code 32 being the injection pump resistor issue. I of course checked the harness and used electrical contact cleaner on the two resistors but everything clean and seemingly good made no difference.

I then picked up some 0.25w 1.5kohm resistors and bypassed the stock resistors by just taping the new ones into the plug. Result was the truck definitely put down more power and rolled a fair bit of coal, but with the beige (fuel supply) resistor being corrected it just ran way too hot, EGT'S were good but coolant temp ran way high. I got rid of that resistor and plugged it back in stock but left the timing corrected and now on acceleration it kicks out some soot but nothing crazy (still has a tad more power) but doesn't overheat.

However it does still limit at 2200 and have a major lack of power up top. I did do some digging and that code 32 can still be caused by a faulty ECU so all fingers seem to point to the same thing now. There's a few shops around Guatemala that seem pretty solid for rebuilding circuit boards (they fix everything here and well) so I'll be looking into getting some work done. I would like to do the caps myself by my soldering skills just are not trustworthy enough to touch something so delicate. There is a shop not too far that rebuilds computers and specialize in small circuit repair so fingers crossed.

 

[Tigris]

Hey thanks guys for all the helpful info, yeah I am alone on adventure on YouTube.

Since I posted that I did go ahead and try some things running with code 32 being the injection pump resistor issue. I of course checked the harness and used electrical contact cleaner on the two resistors but everything clean and seemingly good made no difference.

I then picked up some 0.25w 1.5kohm resistors and bypassed the stock resistors by just taping the new ones into the plug. Result was the truck definitely put down more power and rolled a fair bit of coal, but with the beige (fuel supply) resistor being corrected it just ran way too hot, EGT'S were good but coolant temp ran way high. I got rid of that resistor and plugged it back in stock but left the timing corrected and now on acceleration it kicks out some soot but nothing crazy (still has a tad more power) but doesn't overheat.

However it does still limit at 2200 and have a major lack of power up top. I did do some digging and that code 32 can still be caused by a faulty ECU so all fingers seem to point to the same thing now. There's a few shops around Guatemala that seem pretty solid for rebuilding circuit boards (they fix everything here and well) so I'll be looking into getting some work done. I would like to do the caps myself by my soldering skills just are not trustworthy enough to touch something so delicate. There is a shop not too far that rebuilds computers and specialize in small circuit repair so fingers crossed.

Hi Max,

Just started watching your series on YouTube. Beautiful work. I'm subscribed!

About recapping the ECU. Since your caps have yet to physically leak, recapping the ECU would actually be rather straight forward with a little patience. This job is only hard if you don't have the basic resoldering tools and no patience. Now if you have damaged traces due to caps leakage that would be a different story.

My understanding of the capacitors' issue is that even if they were still not showing any signs of physical leakage, they could almost certainly be compromised still. Electrolytic capacitors behave erratically as they fail long before they leak, and sometimes, they just won't even leak.

In fact, according to a knowledgeable source (Paul Carlson from Mr. Carlson's Lab on YouTube) the majority of the available capacitor checkers (meters) will show a faulty capacitor to be within specs when if fact it's long gone bad. Only very sensitive equipment can verify such faults, but again, good, modern and genuine capacitors are really cheap so no real need to check the ones in service anyway.

Maybe find a reliable shop to recap the ECU while you are traveling and you can have it recapping nice and proper with certified caps once you are back home. Just a thought.

Cheers!

 

[Black94Prado]

Hi Max,

Just started watching your series on YouTube. Beautiful work. I'm subscribed!

About recapping the ECU. Since your caps have yet to physically leak, recapping the ECU would actually be rather straight forward with a little patience. This job is only hard if you don't have the basic resoldering tools and no patience. Now if you have damaged traces due to caps leakage that would be a different story.

My understanding of the capacitors' issue is that even if they were still not showing any signs of physical leakage, they could almost certainly be compromised still. Electrolytic capacitors behave erratically as they fail long before they leak, and sometimes, they just won't even leak.

In fact, according to a knowledgeable source (Paul Carlson from Mr. Carlson's Lab on YouTube) the majority of the available capacitor checkers (meters) will show a faulty capacitor to be within specs when if fact it's long gone bad. Only very sensitive equipment can verify such faults, but again, good, modern and genuine capacitors are really cheap so no real need to check the ones in service anyway.

Maybe find a reliable shop to recap the ECU while you are traveling and you can have it recapping nice and proper with certified caps once you are back home. Just a thought.

Cheers!

Right on yeah thanks tigris and everyone else for all the feedback and help. If i can't find anyone trustworthy enough to rebuild the ECU I'll do it myself. Otherwise for right now Guatemala seems to be an absolute mecca for Landcruisers, they're just everywhere here and luckily with the other landcruiser overlanders I've got a few sources to tap into for parts and specialists. We'll get her back in running order here soon

 

[Black94Prado]

Hey guys, i wanted to wait until the truck was all good and whatnot but instead I'll have to pick your brains a bit more. So 4/9 of the capacitors aren't sold here in Guatemala (so they tell me - i found 5). And with that said there's no idea to know where they're coming from... The 1kzte is a very popular engine in this country with the hiace van/busses running them but even with that these guys are all dumbfounded and completely disagree it's an ECU issue - seems they like to swap to manual pumps and delete the ecus...

With that said, i want to come back to the limp mode topic because well, I've been driving this truck all around this country for weeks with this issue including offroading lava fields and i have to say I've noticed some things.

I don't think it's in "limp mode", reason is, if I'm in low range on the t-case or even low on a flat (and second) it will rev out to 3k+ rpm without limit. And it's really sluggish from a stop start....

i guess.... I guess I don't even have any questions but... I dropped the truck off at a welder today, i found an arb front bumper for sale here and he's also building me a custom rear bumper... In the meantime i think I'll pull the drawers and fridge out, check the in tank filter and pull the injectors and have them tested. I don't know this is all weird. But on the bright side I've gotten a lot of help from some cool dudes here.

One has an older lj78 that is swapped from a 2lte to a 1kz with a manual pump conversion aaaand a rhd to LHD drive conversion hahaha. Plus a hood scoop with an intercooler up top. He also has a pretty beastly defender and main guy has a sweet 79 (and a Lancia Delta in his garage i mean what the hell)

 

[Tigris]

That truck is sweet.

I loved the Lava fields video (I have a similar experience driving through a Lava field in Djibouti (eastern Africa) with a new 1KD powered Prado). That was fun! I have a video but it's not as glamorous as yours

Well, I know this might be silly but have you noticed any anomalies when the ECT button is depressed? You should expect your shift points to be changed with that engaged. The reason I'm asking is because I have heard a few complaints from people with what they described as "limp mode" stating that their power output seemed erratic (rpm jumps) with the ECT engaged.

As for the capacitors, that's a bummer. But hey, in my research on this ECU topic I learned that there was a great deal of commonality among the components Toyota (or more specifically, Denso) used in ECUs from that era (early to late 90s), with many of the values being the same, I would imagine it would be possible to identify a cheap (Corolla/Crown/Celeistor/Surf etc) ECU and use it as a donor for the missing capacitors. This is not ideal obviously but since you are far from Digikey's reach you may get lucky and have something to fill the missing caps for the time being.

Now pressure testing and re-shimming the injectors is always a good idea, so is cleaning the sock filter in that tank. Shi**y fuel is known to cause such symptoms afterall.

Let us know how it goes. Stay safe!

 

[Rigster]

these guys are all dumbfounded and completely disagree it's an ECU issue - seems they like to swap to manual pumps and delete the ecus...

I have a little problem with the logic in the above statement.

If they disagree with it being the ecu, why are they commonly removing the ecu and changing over to manual injection?

At least you have very cheap labor there!

 

[Black94Prado]

That truck is sweet.

I loved the Lava fields video (I have a similar experience driving through a Lava field in Djibouti (eastern Africa) with a new 1KD powered Prado). That was fun! I have a video but it's not as glamorous as yours

Well, I know this might be silly but have you noticed any anomalies when the ECT button is depressed? You should expect your shift points to be changed with that engaged. The reason I'm asking is because I have heard a few complaints from people with what they described as "limp mode" stating that their power output seemed erratic (rpm jumps) with the ECT engaged.

As for the capacitors, that's a bummer. But hey, in my research on this ECU topic I learned that there was a great deal of commonality among the components Toyota (or more specifically, Denso) used in ECUs from that era (early to late 90s), with many of the values being the same, I would imagine it would be possible to identify a cheap (Corolla/Crown/Celeistor/Surf etc) ECU and use it as a donor for the missing capacitors. This is not ideal obviously but since you are far from Digikey's reach you may get lucky and have something to fill the missing caps for the time being.

Now pressure testing and re-shimming the injectors is always a good idea, so is cleaning the sock filter in that tank. Shi**y fuel is known to cause such symptoms afterall.

Let us know how it goes. Stay safe!

Haha man those were the coolest vids I got in a while, you should see the green grass growing out that black rock dust, looks like Iceland almost. Gonna put a full vid on that up soon.

But yeah hey good idea with the old Toyota ecu's I might just try that, it's been a real headache... But hey i mean... I guess it's still running? And its gonna look cool with the bumpers...