I've been plagued with getting code #17 (S5 NA) when I'm driving on the highway, and thinking it was a wiring issue or a bad O2 sensor, so I replaced it and redid the wiring, and I'm still getting it. So I check the voltage on the new O2 sensor and its reading .15 volts at idle, which IIRC means super-rich (it's been rich lately but not that rich).

Does that mean the O2 sensor is bad (destroyed by the fuel?) or is it just reading that low due the richness?

I don't think my wallet can take much more of this reduced mileage on the highway, lol. I used to get like 24 MPG and now I only get about 20.

 

Did you mess with the fuel settings?

 

Never mind, it seems to pull about .6 V, which I think is closer to normal.

 

So if the new O2 sensor is to spec, and there's no apparent shorts or accidental grounds, why the fudge do I get code 17 (which means the voltage is under .55 for 80 seconds)?

It generally only comes up at highway speeds and generally after numerous miles of driving. And it only comes up after your cruising at a constant speed.

 

or are you on stock ECU.

I've had code 17 pop up on me, but it was only in a specific situation.

 

ACV and airpump or none of either?

And .15vdc is lean.

 

I figured that out. But apparently it's supposed to be low at idle due to the air pump.

And it seemed to be .6 when I gave it some gas and lower when I let off.

I have both the airpump and ACV. And the ECU is unaltered.

Keep in mind this only happens while cruising so I think the ACV's air dump and idle readings are irrellavent except to say whether the sensor is good or bad.

The manual says check the spark plugs so I guess I'll do that. They're not very old though.

 

Edited

Just flat not going into closed loop. Put a meter on the 02 sensor wire at the ECU and go for a drive and watch it as you cruise along.

Have you ever tried the Sensitivity check as shown in the attached jpg? Actually I don't believe you need a meter as they show. Just a LED with one end in the top middle socket and the other end in the lower middle socket OF THE GREEN SIX SOCKET CHECK CONNECTOR NEAR THE BATTERY AREA.

 

No, but it doesn't make sense that a brand-new O2 sensor would be bad. Plus the fix for that is replacing the sensor, and I had the same problem beforehand.

Also, how would you put a meter at the ECU? Use a probe in the harness and a clip to a ground? I would think you'd have to get between the O2 sensor and the ECU to get a reading.

 

The green connector by the battery one of them is for testing O2 sensor like hailers said, I used to have a ODBII or whatever computer/scanner, on the fc it could only do like 8 things but one was you could watch the O2 sensor.

If I remember

Accel = rich
Deaccel =lean
Cruise = Alternates between rich/lean rich lean every sec or two

 

There is a green, six socket connector near the battery called a check connector.

On a series five there are three wires in it (a bit unlike a series four).

One wire is BLACK/WHITE (batt power) and another below it is Yellow.

The Yellow one is spliced in to pin 1D on the ECU. In other words they are one and the same item.

IF a LED is connected to a source of battery power (Black and White wire) for the LED positive wire, and the LED's other wire is put to the Yellow wire in the green, six socket connector, then a person should get the same results as shown in the FSM (the page I posted in my last post).

I've three series four. All three have a LED on the dash connected to the Yellow wire and switched power. When driving, and the car goes into close loop, the LED flashes. When you step on the pedal it lights up steady red and does not flash. When the engine is lean, it does not light up at all.

ON a series four car you need to do more than what is required in that page out of the FSM. You have to pull the TPS plug off and pull the neutral switch plug off (memory on that), IF you are doing this from sitting in the driveway. Driving none of that is required.

But what I'd REALLY do with your car, is go to the ECU and backprobe the 02 wire with a digital meter, AT the ECU. Then go for a ride and watch the voltage reading. You should be able to figure out if it's working right or not (whether the connection from the 02 and ECU is good or not.

Anyway, to give credit where credit is due, this method is just something I read on the FC3S TEAM site quite sometime ago.

 

Somewhat related is the jpg out of the series four FSM. Same Monitor test for the 02 done a little different. They have one pull the TPS plug off and remove the neutral switch plug. The neutral switch can be ignored if one just holds the clutch in and puts the shifter in neutral.

Then on a series four you can rev over ??/1500-1700 rpm in the driveway and the LED or monitor will flash.

On the series five I saw no mention of pulling the TPS plug nor pulling the neutral switch. Lucky people with series five.

This ariticle from the TeamFC3S site gives honorable mention to the 02 output just below the figure of the bright green check connector. Call it the GL wire for unknown reasons. http://www.teamfc3s.org/info/article...odes/main.html

http://www.teamfc3s.org/main/articles.php
That site also has an article on the 02 sensor itself.

 

I know the O2 sensor wire is shielded, but I'm curious what that actually means when it comes to repairing the wire (I used a spade but covered it with electrical tape)...


What does closed loop refer to exactly? I mean, I'm getting voltage and everything, so what does the shielding prevent?

FWIW, I didn't let the shielding touch the signal wire.

 

WOOPS, I guess I DID have the shielding wire touching the signal wires. I cut them further back, taped them, then re-spliced and heat-shrinked the wire. I hope this will finally solve my problem and give me my cruise mileage back.