Jipopotamo

87 22re EFI 5-spd

I'm getting a code 21 and 52. Oxygen sensor and knock sensor, respectively.
I just bench tested the O2 sensor and it is in perfect working order. So that means either wiring or ECU itself correct? Also, the knock sensor itself tends to last forever, correct? That also puts me in the wiring or ECU boat.

What are the pin locations on the ECU itself for these sensors, and a good way to check them at the ECU itself before I decide to rip through my main harness following the wires themselves. I checked the upside, I'd like to check the downside now, and then I suppose I'll have to check everything in between.

Jipopotamo

Doing some more searching and reading, I'd like to add some more relevant information.

I cleared the computer by pulling the fuses and started fresh to see what the computer threw out.
Right away, it was throwing a code 21, oxygen sensor, and that was it. After running the engine for awhile, it was still only code 21. After I pass 2000 rpms, the code 52 shows up as well as a code 42, vehicle speed sensor.

First question, if the O2 sensor is irrelevant to the engine at initial cold start up, how or why is the ECU telling me right then and there that the O2 sensor is bad? Also, the fact that the sensor itself benchtested ok. Methinks this means bad wiring, as in the wiring is already grounded out somewhere and instantly triggering the code 21.

Since the code 21 would effect the fuel and running conditions of the engine, could it be inducing enough of a pinging to then trigger an actual true code 52 reading?

And the code 42 has never shown up until just recently, even though the vehicle has no road miles on it to give it relevant information regarding vehicle speed in my mind.

I'm just getting broken by this mess. I want the truck to be happy.

allnmstkn313

If the O2 sensor isn't connected it will immediately toss a code, that I know for sure. My gut feel would also be that the knock sensor is being triggered by the off mixture pinging.

I'd focus on the O2 wiring first... Wiring gremlins are just a bitch.

No ideas on the speed sensor, sorry.

Jipopotamo

Hey now, that's plenty good info there All. i appreciate it. That's exactly how the computer is behaving. Complete wiped memory and the code 21 is immediately present. Sounds like it thinks it isn't connected. Wiring oh wiring, here we go.

Jipopotamo

Ok, got Homer the ohm'er out today and checked my O2 wire for continuity from the engine bay connection to the ECU connection and it checked out ok. That means I have now checked the O2 sensor itself, and the wiring from the sensor to the computer. Both of those checked out fine and I have a code 21 from the computer consistently. Does this mean my computer is conked out? Any way to test the ECU itself for results?

4runner530

real quick I know this is off the subject but does anyone know where the ECU is located in my 95runner I am trying to find it to program a keyless remote

VegasNaturist

Did you check both sides of the O2 sensor (heater and main)? This assumes (yea, I know) you have a 4 wire sensor. On the code 52. I had this problem recently. Code would come up as soon as the rpm's passed 2K. Checked the wiring to the ECM, and just for craps and giggles replaced the connector at the sensor. No joy! Found a new sensor on Amazon.com for $135. and installed. Problem fixed! Code 52 means the ECM is NOT getting an input from the sensor. The code does not indicate the presence (or lack of) a ping. IAW the ECM can't tell if the engine is pinging or not. So, to answer your question, no the sensor doesn't last for ever...

John

Jipopotamo

Thanks Vegas. I have a 1-wire O2 sensor.
The knock sensor itself may be no good than, I'll check into that. The first step I'm paying attention to now is the presence of a code 21 (oxygen sensor) on a cleared computer memory without relevant information to know if the O2 sensor is even bad. Also, the fact of bench testing the O2 sensor as good and the wiring from sensor to computer as good leads me to suspect my computer. I just put up another thread dealing with just the computer and some pictures as my computer is stamped as a 22R unit, but I have an 87 matched 22re block and head. Oh, woe is me.

VegasNaturist

Not sure about an '87, but my '89 has a (actually 2) 4 wire O2 sensor. Mine is CA emissions. Anyway, 2 wires are for the sensors heater, one is for the sensors signal, and one is for the ground. The code indicates an open or short in the heater circuit or the signal circuit. You might want to check to see if a 4 wire sensor was replaced with a generic 1 wire sensor. Poke around where the sensor is under the truck for more wiring.

Don't get discouraged though. I just recently bought my truck and have put over $800 in it trying to get it right...

Reman injectors = $100
Reman VAF Sensor = $175
Knock sensor = $135
New Head, gasket set, head bolts = $349
Plugs, cap, rotor, misc stuff = $100

The PO's trusted mechanic JB welded the #1 spark plug into a stripped hole. Didn't realize it till I tried to replace the plugs. Could have tried different ways to repair said hole, but decided on replacing the head instead. So I hear ya when you say woe is me...

John

rustypigeon

I don't have a FSM handy, but I thought a code 21 was for the heater function for the O2 sensor. That would mean 4 wires though.

Somebody have a FSM on hand to confirm this?

Jipopotamo

It's for the O2 sensor signal/O2 heater circuit signal.
But as I said, I only have a one wire O2 sensor. And the ECU is a confirmed match for my truck/engine/wiring harness, it only wants a 1-wire O2 sensor.
It's to the point now where I took the truck driving for a long while yesterday and let the new engine get nice and settled. I am perfectly content with the driving condition as of now and to hell with the codes at this point. I am moving in about two weeks and just need the truck to be able to make the 180 miles from point A to B and it will now. So I'll just wait til I get my shop set up in new place and then I'll figure this mess out.