No CEL light

[94cruiserchick]

I have been having problems with my 94 missing so I took it to get it scanned at Oreilly's even though I didn't have a check engine light and the tool said vehicle not responding. We tried the paperclip trick and nothing came of it. I am now thinking that a previous owner decided to cut the wire for the check engine light. It doesn't even appear when the truck is on but not started. I read through the wiring diagram but it is all jibberish to me. I would like to know where this wire runs to and from and where should I start looking for a cut so I can get it fixed to get some codes. Or if someone could point in the right direction it would be very helpful.

 

[CruiseOrlando]

It could be as simple as the fact that the bulb was removed.

94's aren't OBD-II, dunno if the guy at Oreilly's knew that or not...

I'd take the dash apart and look at the bulb. Might have been on so long it burned itself out...

 

[94cruiserchick]

Our Oreilly's had the scanner for Toyota obd1. When he plugged it in it said the ECU is not responding. That is why we think the wire is cut somewhere.

 

[elhombre]

You are probably looking at two different problems. First, I would be suspect of O'Reily's scanner. Most of those monkeys at the chain part stores are at the top of their career ladder and only know what their computer tells them. You need to have it scanned by a known scanner that works on your Toyota.

How bad is it missing? Is it something that new plugs, wires, distributor cap, and rotor will fix? Or is it a case of no power with an obvious cylinder not firing at all? If it is the first situation, the computer will most likely not throw a code anyway.

 

[3800cruiser]

You are probably looking at two different problems. First, I would be suspect of O'Reily's scanner. Most of those monkeys at the chain part stores are at the top of their career ladder and only know what their computer tells them. You need to have it scanned by a known scanner that works on your Toyota.

How bad is it missing? Is it something that new plugs, wires, distributor cap, and rotor will fix? Or is it a case of no power with an obvious cylinder not firing at all? If it is the first situation, the computer will most likely not throw a code anyway.

I am helping out with this fix. When we were at the store, this is the scan tool that was used. It is supposed to work for Toyota / Lexus 91-95. I don't think all stores do this, but the manager is a close friend so he always helps me out the best he can. Money's a little tight right now so we need a good scientific, specific diagnosis and can't play parts roulette.

If we're going to talk about the misfire in this topic:

SYMPTOMS:
*The exhaust "Smells" rich
*After the engine is warm, it stumbles/has no power at idle and when accelerating to about 2500 RPM. Above 2500 RPM, it smooths out.
*No Check engine Light
*Runs like a raped ape when the engine is still cold
*Not seeing any smoke out of the tailpipe other than some residual oil from time to time from valve stem seals leaking.
*PRND32L lights do not work, reverse tail lights do not work either
*Last night the stereo amplifier started making static so I unplugged the power going to it to stop the static and the truck seemed to run a *little* better, as strange as it sounds. This leads me to believe I need to check the wiring to the ECM behind the glove box, which I'll get to in the next few days.

WHAT WE'VE DONE SO FAR:
*The dizzy cap/rotor is clean and not leaking any spark,
*The coil is good,
*the plugs are fairly new,
*Plug wires test good with a multimeter. No arcing is present either.
*The engine harness by the EGR stovepipe is fine and I have added extra heat sheilding to it as a preventative maintenance item.
*Tonight I will be checking the ecu harness in the cabin.

 

[CJF]

If we're going to talk about the misfire in this topic:

I wouldn't...

 

[CJF]

Money's a little tight right now so we need a good scientific, specific diagnosis and can't play parts roulette.

Then you need to get the CEL working, period.

Whatever that scan tool said is non-information. Start by assuming the bulb is burned out. If that turns out not to be the case, then go from there.

 

[3800cruiser]

Then you need to get the CEL working, period.

Whatever that scan tool said is non-information. Start by assuming the bulb is burned out. If that turns out not to be the case, then go from there.

Planning to do some work behind the dash panel anyway, I'll pull the cluster while I'm in there.

 

[jonheld]

When we were at the store, this is the scan tool that was used.

There is no "scan tool" for an OBD1 vehicle. There was no standard for OBD1 between manufacturers. OBD1 ECUs couldn't display information that can be read on a scanner.

The correct method for reading ECU fault codes on an OBD1 vehicle was to short 2 pins together and interpret the blinking lamp. That's how the ECU displayed codes in memory.

If your truck starts and runs but the CEL is not illuminated with the key in the ON position without the motor running, then the bulb is burned out or removed or possibly covered with black tape to mask a potential problem before a sale or to avoid automatic rejection when going for an inspection.

 

[ssbob]

On my 93

The PO took the bulb out, when I put it back in all sorts of codes showed up. Still fixing them today.

I would assume that either the bulb burned out or the PO removed it.

--Sean

 

[CruiseOrlando]

My guess on your problem: O2 sensors. It's not a cheap 'parts roulette' thing, however, and concur that the first thing is to get that light working.

 

[94cruiserchick]

My guess on your problem: O2 sensors. It's not a cheap 'parts roulette' thing, however, and concur that the first thing is to get that light working.

We have thought that the o2 sensor may be bad, but when we tried to pull it to look we couldn't get it out. But this weekend, if not sooner, we will pull the gauge cluster and check the bulb and go from there.

Thanks for all the responses and giving me some insight.

 

[94cruiserchick]

The light is now working, the bulb was burned out. Finally got some codes.
28- number 2 o2 sensor
41- throttle position sensor
71- egr system.

 

[CruiseOrlando]

Ding ding ding!

Heat will help get that O2 sensor out. Along with some damaged bolt removers. That's what it took for mine.

The 71's *might* be cured by Seafoam (a few cans, to be sure), along with the 41. All depends on the details. The EGR is a fun one to track down... money pit comes to mind...

 

[86tuning]

There is no "scan tool" for an OBD1 vehicle. There was no standard for OBD1 between manufacturers. OBD1 ECUs couldn't display information that can be read on a scanner.

Toyota dealership has a thing called the TDT Toyota Diagnostic Tester that can be used with obd1 cars.

But yea, blink codes are fast n easy and require a 2cent paperclip vs hundreds or thousands of dollars worth of equipment. Basically tells you the same thing.

 

[94cruiserchick]

Ding ding ding!

Heat will help get that O2 sensor out. Along with some damaged bolt removers. That's what it took for mine.

The 71's *might* be cured by Seafoam (a few cans, to be sure), along with the 41. All depends on the details. The EGR is a fun one to track down... money pit comes to mind...

Do you think there is any way to clean the O2 sensor?
As for the EGR system, it's been broke since I got the truck, if I do anything it'll be take the thing out and block it off.

 

[Mark W]

Seafoam is snake oil and will not solve any problems. 02 sensors cannot be cleaned and simply must be replaced.

Fix your O2 sensor first. A bad O2 sensor can play hell with how the vehicle runs. Then clear the codes and see if the e.g.r code comes back. It may not. If it does, the first thing I would check with the vacuum lines which actuate the valve. I have seen them pulled lose or misconnected more than once.


Mark...

 

[CruiseOrlando]

Sea Foam isn't snake oil. It fixed my EGR issues. Took about 4 cans of the stuff, but it fixed it.

It got back 3MPG on my dad's 08 Minivan, and it got back 10% of my fuel economy on my G35. Definitely NOT snake oil, but it's also not a cure-all. It helps. The only thing that truly fixes things is cleaning and/or replacing parts in the EGR.

As for cleaning the O2 sensor, yes you can clean them. However, lots of times those things are so rusted on that you'll need new hardware to put them back. It's not expensive, but it's something you should be aware of before you take them off.

 

[3800cruiser]

Sea Foam isn't snake oil. It fixed my EGR issues. Took about 4 cans of the stuff, but it fixed it.

It got back 3MPG on my dad's 08 Minivan, and it got back 10% of my fuel economy on my G35. Definitely NOT snake oil, but it's also not a cure-all. It helps. The only thing that truly fixes things is cleaning and/or replacing parts in the EGR.

As for cleaning the O2 sensor, yes you can clean them. However, lots of times those things are so rusted on that you'll need new hardware to put them back. It's not expensive, but it's something you should be aware of before you take them off.

Seafoam has done wonders in several of my other vehicles as well for getting soot out of things. I do know that if not used sparingly it can wreak havoc on 02 sensors and catalytic converters.

We are going to search the junkyard this weekend, hypothetically, as long as it's a toyota 4-wire oxygen sensor and the fitment/dimensions are the same I'm thinking I can wire one in even if the harness isn't the same by using the old 02 sensor's plug. I'm having trouble finding a good interchange list anyway. We're also going to try soaking the 02s in some gas to get the crud off. I think they're probably caked in oil residue as the truck needs valve stem seals and it'll be a short matter of time before they will need another cleaning or replacement.

The TPS may just be gummed up, I had to clean the throttle body for the blade sticking a while back and got everything clean but the TPS. I couldn't get the TPS out because of the confounded bottom screw, will have to try it again.

 

[CJF]

We are going to search the junkyard this weekend, hypothetically, as long as it's a toyota 4-wire oxygen sensor and the fitment/dimensions are the same I'm thinking I can wire one in even if the harness isn't the same by using the old 02 sensor's plug.

That's a *really* bad idea.

O2 sensors are like sparkplugs: they wear out over time, period. (Owner's manual recommends replacement every 80k miles.)

No way would I do *anything* other than replace both of them (not doing so is like only changing 3 of the 6 sparkplugs) with brand new OEM.

Good luck,

Curtis