I should have a chance to look at at the FSM later this week. We've had a silly issue forever with small differences between US & Canadian cars. This may be one of those. I think you're correct in that it's for something other than a varying temp sensor.

It's quite possible to have a thermistor ...

I did say #8... that happens every so often - Senior Moment. Of course it's #6. The gauge cluster (IPC) would be fed by the BCM, which would get it's temp info from the PCM. The sensor in question has just one wire, but the connector has the facility for 2 wires, but not in this application. The ...

It's between cyl #8 & the throttle body base, on the same plane as the coolant sensor & directly under the fuel pressure regulator. Can't miss it.

Geoff

The a/c pressure sensor is usually fitted into the a/c accumulator, nowhere near the engine. It turns the a/c clutch on/off when a/c pressure is in/out of range. If the a/c system runs too low on refrigerant, a/c pressure will be too low so the clutch can't be engaged, thus protecting the system ...

J Wikoff
You are quite correct of course re the 2 sensors. I'm pretty sure that the single wire sensor is related to either/or both the a/c & rad fan. The Mitchell diagram shows an a/c pressure fan switch running to D9 (603) with a Dark Green-White wire, which is exactly the colours on the second ...

J Wikoff , thanks for the response. I believe you are right. It doesn't make much sense to have both. I'll have a chance this week to look at a GM manual, but it would be nice to confirm it before then.

There is a sensor in the intake manifold, but it has just one wire and it looks like a ...

Gentlemen,
I'm wiring up my 92 3800 S/C engine getting it ready to drop into my Lotus Super 7. I have an issue that maybe one of you can throw some light on. The only wiring diagram I currently have access to is a Mitchell. I may have the wrong diagram, but it's the only one available in On-Demand ...

for Mechanical Mike

What's your point?

Geoff

There's something to learn in all of this. I just re-read some of the early responses and it goes like this:

Feb 2 charliemax spots a discrepancy with the MAP values at higher throttle pos.
1fatcat asks "is this since storage"?
I commented charliemax is on the right track

Feb 3 charliemax asks ...

'95 and earlier vehicles are 1st gen OBD(I). There was no rear O2 sensor, and no facility in the PCMs/ECMs to read the cat's efficiency. Those systems were/are extremely simple relative to OBDII vehicles in terms of programming and diagnosis, especially self-diagnosis. They didn't run complex self ...

I know zip about aftermarket tricks to fool the PCM, but I can't imagine any of them being able to emulate the changing voltage signal that the rear O2 supplies. The PCM is continuously testing every component remotely related to emissions.

There are 3 Continuous Monitors, (and usually 6/7 Non ...

Hi Oldman,
Don't feel too bad. Lots of experienced techs don't REALLY know what they're doing either in that department. OBDII is a VERY complex system. Anyone that says they know it all is fudging the truth. Even the best trained dealership techs have to go to their manuals to follow complex ...

I didn't ask, I was a little embarrassed at jumping to a wrong conclusion. The engine noise in it wasn't a major problem apparently. If it's of more than passing interest I'll ask him. He's got a week in the Dominican so I won't talk to him until then.

I just wanted to set the record straight ...

You're quite welcome, glad to share. Re a good Cat. The original is the best way to go, but obviously way costly for what you get. I'd ask a local tech that's involved in both test & repair what's the best available for the price.

I think I'd tend to stay away from muffler shops, unless you know ...

Merrillspontiac,
You were absolutely correct re the '00 Monte Carlo. It wasn't an L67. Something got lost in the translation between Rob (The GM Tech) and me, when he said he had another coming in with a knock, in the same conversation as the '99 Buick L67 with the knock.

Pardon the confusion ...

For a little clarification. The PCM's primary functions are to protect the cat and to produce an average air/fuel ratio of 14.7 parts of air to 1 part of fuel -(by weight) stoichiometric. Throughout all of the changing conditions, from cold to full warm & idle to WOT, the PCM is collecting ...

You asked for a Professional opinion, here goes:

The Cat Efficiency code is caused when the REAR O2 sensor spends too much time reading above 500mv (rich). This is almost exclusively related to the condition of the Cat. When a good cat is operating correctly, the rear O2 will read below 500mv. In ...

Merrillspontiac, you may be correct re the Monte Carlo engine - can't say. It didn't show up yet at the shop, I was there this morning. The owner had said it was knocking loudly, so I imagine it'll be there at some point. I'll certainly get a look at it then and let you know.

Geoff

Hi Guys,
It was a LeSabre for sure. It may? be something to do with it being a Cdn car, we get a lot of that. The L67 is used in a lot of places I didn't expect. My friend with the blown '99 has a 2000 Monte coming in tomorrow with a "knocking sound", it has the L67 too. It must be the season.

The ...

Somewhere below 4000rpm, the PCM cuts the S/C out. The MAP readings taken @ WOT are of little use to assess S/C operation. I got this from a GM tech last weekend. I don't want to get back involved with this car, but I hate to see you guys potentially chasing your tales. Check out a known good ...