Mark Davis

Hello All

I just purchased a 1994 4Runner with the 3.0 V6. And wouldn't you know the CEL comes on the next day. I pulled the codes with the help of a freind and this is what we came up with 2, 5, and 12. I am planning on changing the oxygen sensor this coming week end and I will see if that makes a difference. We also noted that the Over Drive light was flashing with the CEL. I did a search and found that this has happend to some one before but I could not find the reason for it. Should I be worried by this. The truck has 113K on it and the head gacket was done at 92K. Over all I am very pleased with the purchase except for the bulet hole we found under the molding on the passanger door. Any thoughts on the flashing OD light would be welcome. I will try and post pictures on Wednesday.

Thank You
Mark

toyota_mdt_tech

I doubt it was a 2 and a 5 followed by a 12, I'd bet its a code 25. But technically, the code 12 should of shown up first. I suspect code 12 is the starter signal, ignore it. Code 25 is lean, I'd bet you your injectors need to be cleaned.

infiltrator

search for here on information about seafoam, and run that in your brake booster line :]

toytech76

I wouldnt suspect an injector for a code 25. i would check your o2 sensor sweep pattern first then pending those results I would do a compression test. ignore code 12. They all have that

CILO

Hi toytech, what exactly is an o2 sensor sweep pattern and is it possible to do a compression test with the intake manifold taken off?

thanks

toytech76

The sweep pattern shows how the o2 sensor is switching back and forth between lean and rich. A shop with the right equipment for veiwing OBD 1 info should be able to do it. I guess you could do a comp test with the manifold off but why would you take it off in the first place? Your flashing o/d lite I believe indicates a transmission problem

Mark Davis

Thanks all I just went out and re checked the codes here is what I have the CEL is giving me codes 12 and 52 and OD light is giving me a code 63 for the transmission. For the engine the list says it is a Knock sensor is this easy to replace. For the transmission the code 63 is for a severed #2 solenoid or short circuit. I have never worked on a transmission before is this something that I can tackel.

Thank You

Mark

toytech76

The knock sensor is labor intensive. The whole intake system needs to be off since the knock sensor is in the valley. Get a sensor and a knock wire or if you arn't comfortable take it to a shop. The trans you hafta drop the pan and i'm not sure if the solenoid is behind the valve body or not. Might wanna go to a trans shop

mattches

Sounds like the person who sold it to you reset the ecu just before letting you take it. If it is a knock sensor, it is a big PITA to get to and it is pricey (120+). You have to remove your intake plenum and all associated fuel, exhaust, vacuum, electronic & coolant hoses from the throttle body & plenum (be sure to take pics and label them well. Then off comes the fuel rails (don't lose the crush washers on the fuel rail!), injectors & intake manifold (new gaskets are pricey too). The knock sensor is right in the center of the galley and is pretty evident. It comes out with a large socket. However, it could just be the wire. Wire is only like $7, run a continuity test and ohm test on the wire, could save you some big $$. To replace one or both, they must be purchased from the dealer. I found a knock sensor online from some dealer out east for $123 and the wire as well.

Since you are that far into your engine, be sure to check the coolant hoses on the back of the motor (to the heater) and associated thermal & electronic connections, the valve cover gaskets, condition of your fuel injectors, timing belt, idlers, and freeze plugs while you are there. Replace as necessary.

Good luck!

Mark Davis

I found this post

Chances are that your O2 sensor is causing both codes. If your O2 is giving a rich condition all the time then the ECU will try to lean it out even though it is not rich. This may cause exsessive spark knock which will give a knock code. I would change the O2, reset the ecu and see what happends

Does this sound possible. It would be a lot easier to switch out the O2 sensor. Also I have been pricing O2 sensors and they tell me that I have two of them. The 4runner is a 1994 and came out of California.

Thanks for all the help.

Mark

CILO

Toytech, the reason i asked about the compression test is that i have to test the pair reed. Also, i have to remove and repair that temp sensor with the two nipples as i broke one of the pieces off. I figured since i have the manifold off it would be easy to do a compression test as it would be easier to reach the plugs on the passenger side.

If I'm not mistaken, i think you had suggested doing a comp test as part of checking my code 25 issue. would this suggestion also apply if my code 25 comes and goes?

toytech76

I found this post

Chances are that your O2 sensor is causing both codes. If your O2 is giving a rich condition all the time then the ECU will try to lean it out even though it is not rich. This may cause exsessive spark knock which will give a knock code. I would change the O2, reset the ecu and see what happends

Does this sound possible. It would be a lot easier to switch out the O2 sensor. Also I have been pricing O2 sensors and they tell me that I have two of them. The 4runner is a 1994 and came out of California.

Thanks for all the help.

Mark


No..an o2 sensor would not cause a knock sensor code. The code comes up only if there is a fault not because the sensor is working off any rich or lean condition.
The plugs on the pass side are easy enough to get out with the plenum still on the car. Use a long extension and a wobbly plug socket. If you try to run a comp test with the plenum off you will throw a check eng lite plus gas will go everywhere since your cold start injector is undone. If your code 25 comes and goes its more likely just the o2 sensor. Not a bad idea to run a comp test anyways and have your valves adjusted if you havent in the last 60K. If you are gonna replace your knock sensor, replace the sensor and the wire since you are in so deep. Cheap insurance

Mark Davis

Thanks for all the help. I have taken the truck back to the dealership I bought it from to have it fixed as it is against the law to sell a car that will not pass DEQ. I hope this works out.

Mark

CILO

"If you try to run a comp test with the plenum off you will throw a check eng lite plus gas will go everywhere since your cold start injector is undone."
Good point toy. Common sense isnt on my side today, lol.

Anyhow, if there's a possibility of there being a short in the wire that runs from the O2 sensor to the ecu, would that cause the ecu to think the engine is running lean?

this code 25 had gotten the best of me. I had checked everywere for an air leak and found none, gas pressure is within speck and ignition components have recently been replaced along with the o2 sensor. thats why i figured i'd check the pair reed for any leaks or a binding valve, my guess being that air is being pulled in through there and giving the o2 sensor a false reading. Would this be a valid guess?

thanks again Toy

toytech76

Again, if you have a code 25 even after your o2 sensor has been replaced your next step should be a comp test. All cylinders should be within 10% of each other. You might have a tight or beginning to burn exhaust valve giving you that code

CILO

Thanks Toy,

Once this cold spell passes I'll be checking my compression and see what I get

toytech76

good luck!