Check Engine Light

[Rex]

Tonight on the drive home, my check engine light came on while doing 75. I drove the rest of the way home (approx 10 miles) with no signs of trouble, other than the light .

No signs of uneven or rough idle, the "tone" of the motor didn't even change as the light came on. I just happened to glance down for a review of the cluster as it light up. Any way I can see what brought it about or is this a mandatory trip to the dealer?

[DAEDALUS]

How to check codes--posted by Elwesso in a recent thread:

I did it myself...... You take out the ECU, do this little thing with a screw, and the computer blinks the codes......

Search around the full procedure is there, but here is a crash-course......

The passenger side kick panel is where the ECU is located (its right next to the speaker on the car, not the door).... There is a nut holding it in place near the firewall, so undo that..... The panel comes right off...... next, there is are two screws holding it on, one on top and on the bottom, on the connector end of the ECU..... undo those, and it should come out..... I had to undo the connector... Just loosen the bolt (it doesnt come out), and pull out the connector, being careful to pull it out straight..... From there, you just pull out the ECU, and plug it back in...... The plastic screw is on the front, and turn it clockwise, wait at least 2 seconds, then counterclockwise.......

Then the red LED on the ECU should come on, end then you simply count the flashes..... There is about a 1/2 second in between codes, so have a pen and paper ready.....

The long flashes are the first digit, and the short ones are the second digit....

Knock sensors are code 34, so it would look like __ __ __ _ _ _ _

Then there is a slight pause, and then it goes to the next code.....

You can also check your o2 sensors from the ECU...... I can post that if you'd like......

[Q45tech]

Luckily there are so few codes on ECU that light the check engine light that at least you know it is something serious. ...........95k? O2 sensor/EGR.............Ohio oxygenated fuels?

[Rex]

Okay, through some careful and tedious work I have the ECU on the passengers floor, I turned the "screw" and got no codes. So the "idiot" question is do I have to have the key in the car? And if so, what positin does it need to be in?

THANKS

[Touchdown038]

You have to have it "On" I believe.

[Rex]

34 and 45

[Q45tech]

34 is knock sensor or knock sensor harness45 is injector leak or failure of O2 sensors to switch properly showing a rich condition.Change both o2 and see if it goes away, before removing the plenum.............kind of a $300 job vs. A $1500 job...........but after 10 years probably time to R&R the plenum hoses KS, etc.

[Rex]

If there's a thread on this already, please point me in that direction as a search for o2 sensors didn't turn up and "how to" info.

Is this a DIY? and since I don't have a FSM, what would be the best source short of waiting lonmg enough to get a FSM?

[DougQ45]

Rex: I was going to reply earlier, but wanted to see your code number. Do a search for Code 45 injector leak. Had the same thing a couple of weeks ago which was corrected by replacing the O2 sensors. Good luck.

[911/Q45]

If the idle isn't rough, it's unlikely that an injector is bad.

[elwesso]

Go through and ohm all the injectors...... Good preliminary start.... They should all be 11-14 ohms...... Now is a GREAT time to go out and get a digital multimeter... I got a good one at walmart for 15, and it has already paid for itself.....!

If your getting the CEL, the injector is failing the resistance test... Doesnt necessarily mean that its bad, but its on its way....... Do a search on testing injectors...... Dae posted something about how you can undo a harness and individually test all the injectors.......

[Q45tech]

"If your getting the CEL, the injector is failing the resistance test... Doesnt necessarily mean that its bad, but its on its way"

Wrong the ecu is just seeing a richer than normal AF ratio because the O2 are slow switching.........the ecu can't check the injectors resistance......it is just programmed to throw a code/light.

The knock sensors may still be bad and you will have to check for codes every week because they will not light the CEL.

[elwesso]

:oface:

Thats what I get for commenting on something that I dont know much about......

[Rex]

Can anyone give me an idea of what "book hours" are for replacing the o2 sensors? and if any special tools are needed?

While I'm at it, part numbers (94Q, TCS, non-active, non-CA)?

Also, any "damage" if I drive it for a week or 2 (<250 miles, under 50mph) while I wait on parts and time?

THANKS

[elwesso]

Shouldnt be any damage that I can think of....... It may smoke a little (running too rich).......

Goto http://www.sparkplugs.com and order there...... You want the NGK ones......

Its more or less a daunting task than it is hard.... You'll want a "crows foot" wrench to get to it........ Id say maybe an hour......

[Q451990]

I doubt a week will kill it, but having a bad O2 sensor and running too rich can damage the very expensive pre-cats. Dennis has mentioned in some other posts that the 94+Q pre-cats may be made of a different material and be more prone to melting/clogging. The more I think about it, the more I'd park it until it's fixed or you're taking it to the shop. I've removed mine with a standard O2 sensor socket and a string of extensions. It involves a little work pushing the extensions up through the gap between the engine and firewall, but it can be done that way.

Heath

[Q451990]

As far as parts - many members are happy with the NTK sensors from http://www.sparkplugs.com

I did a lot of research on this very issue last week searching for Bosch replacements - the OEM units say "JECS LIC. BOSCH" on the side, but couldn't find anything I was particularly comfortable with. After about four hours on the internet and phone I finally gave up and just ordered OEM from Joe. $103 each.

Heath

[DougQ45]

Just finished putting the Sparkplug.com replacements (sorry Joe) in my 94 for about $53 each. You will need a very skinny *** forearm to reach up and disco the little plastic wire "ties", a special "o2 socket" to remove the 02 sensor unit , universal joint for your ratchet, several extensions to ratchet, ramps to support car while you contort your body into an unpleasant position that will ruin the next several nights sleep, and about 2.5 hours of time (for both sensors). Dealer will probably quote some very fair price, say about $600??

[Q451990]

Dealer will probably quote some very fair price, say about $600??

Given the pain involved, I wouldn't be surprised.