Baffling Sequence of CEL on 1993 Cruiser (1 Viewer)

Joined
Aug 1, 2017
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Seattle, WA
Hi all. I'm stumped by the check engine lights I have gotten so far in 2020. Maybe I'm just really unlucky, but I might be missing something and I'm hoping one of the great Mud folks far cleverer than I can point it out to me. I'll try to make this brief.

I have a 1993 Cruiser with 311k on it. In April, I got two check engine lights: 21 and 52. Oxygen sensor and knock sensor. Well the wiring harness for the knock sensor was completely ruined so I replaced that and I replaced the oxygen sensors and I was good to. No CEL for over a month. Then in May I was doing some off-roading and went through some reeeeaaally deep water, like up to the engine latches. Got out fine but about 5 minutes later I got another CEL: 26. Chased the problem down for a weekend and ended up solving it by replacing the spark plugs with NGK iridium (not sure how the water crossing affected that but I will have to worry about that a different day).

A few days later I was off on a major road trip and doing some hard wheeling when I got another CEL. Pulled the codes: 28 and 52. 28 was a new one but 52 did not surprise me because it was tough to splice the new wiring harness into the existing wire for the knock sensor so I figured that might have been jostled loose on the rough terrain. Seeing as I was on a road trip and did not notice a change in performance, I did not fix them immediately. But I noticed something odd: the CEL would periodically go off and then come back on randomly. Usually it would be on for an hour or so and then off for an hour or so and almost always off at startup. But every time I pulled the codes it was always 28 and 52, never one without the other. I figured it must be a new problem causing both but could not find anything on Mud so eventually I just redid my splice of the wire to the knock sensor and that fixed both! Once again I was CEL free (though I have no idea how that fixed 28).

Until yesterday. The CEL came on again. I pulled the codes: 26 and 52. I can't believe it! I thought I was done with 26 after changing the spark plugs. Drove to work today and the CEL was off. On my way home this afternoon it came on again so I pulled the codes when I got home again and sure enough: 26 and 52.

My questions are these:
1) Are all these issues just unrelated and I am unlucky?
2) If so, any tips on how to do the splice for the knock sensor better so it stays? I tried solder but found it super hard to get the soldering iron into the space.
3) If 26 is for real again, do you think it could be that one of the spark plugs has already gone bad or is it more likely attributable to some other explanation like a vacuum leak?
4) Should I do anything about 28 or just forget about it since it is gone for now?

And most importantly:
5) Is there anything that could be related to all these issues, some magic pain point that I can fix and solve the CEL crisis of 2020 for good?


Sorry for the lengthy post.
Looking forward to getting to the bottom of this.
Thanks in advance.
 
Joined
Nov 18, 2019
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Albuquerque NM
If so, any tips on how to do the splice for the knock sensor better so it stays? I tried solder but found it super hard to get the soldering iron into the space.

I put my legs under the axle and sort of sat up in the wheel well. It wasn't comfortable but I was able to solder on a new harness for the knock sensor. Turning or removing the DS wheel might help.
 
Joined
Dec 8, 2006
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9,727
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New Jersey
You never mentioned clearing out the old codes from the ECU.
Any time you are chasing engine codes, you should make certain that the codes are current and not old codes that are stored in memory. If you remove the 15 amp EFI fuse in the underhood fuse box for about 10 minutes, this will clear out any stored codes in the ECU and force the ECU to "relearn" all the sensors.
I do this anytime any sensor is changed or any work has been done under the hood that may effect the ECU. It's the same concept as rebooting a computer.
Any codes displayed after this are current trouble codes.
 
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Olathe, KS, USA
Unlucky.jpg
 
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If 26 is for real again, do you think it could be that one of the spark plugs has already gone bad or is it more likely attributable to some other explanation like a vacuum leak?

One possible source of you're code 26 could be water in the O2 sensor connectors. If you were running through deep water it's not uncommon for the O2 sensor connector on the passengers side of 93/94 LandCruisers to fill up with water. Climb under the truck, disconnect BOTH O2 sensor connectors, dry them out with compressed air, make sure there is no corrosion on the pins, and put them back together. Then you'll need to clear the code in the ECM, drive the truck for a few miles to get it into closed loop to see if this was the source of your code 26 problem.
 
Joined
Aug 1, 2017
Messages
47
Location
Seattle, WA
Thanks for the tips. Did not know resetting the ECU could make a difference--I thought the codes would always clear manually and would not be recurring. At any rate, I just cleared them by resetting the ECU as you described. I have already sprayed the 02 sensor connectors with compressed air and they looked fine to me. We'll see if any codes come back on and if they do I'll try replacing the O2 connectors (if it's 26 or 28) or getting my head in the wheel well to solder the wiring harness for the knock sensor.

I appreciate it.
 
Joined
Feb 7, 2009
Messages
2,506
I had codes 25 26 which is lean and rich new o2s from yota cleated them up and never got again. Look over the o2 harness good might have rubbed a wire over the tranny hump. If you are gonna do a lot of deep water might be good idea to put your o2s up in the manifolds in the engine bay. I’ve had mine there for 4 years or so now been trouble free
 

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