My lovely 84. Once the car heats up I get the most annoying buzzer that wont stop until the car cools. I removed the radio etc. and found what I think is the timing relay. And it has a nice loud buzzer built right in. If I remove the brown wire to relay terminal #31, the buzzer stops. The way I read the diagram, that wire comes from the M193 control unit. What is the timing relay. For that fact. What is the control unit. I don't know what to do now. Could someone offer me some advice?

 

Is it a 'buzz' like an electrical 'buzz'?

or more of a drone/tone?

 

Hey. It is electrical. The buzzer is built into the relay. It's an on-off-on-off...... Till the car cools. Even with the ignition switch on. But the engine running or not. The coolant levels are good and there are no warning lights. Won't reset either.

 

M193 is the option for the Cat Overheat Warning System, normally found only on Japanese models.

Either your cat is overheating, or the system is faulty. There is a thermal sensor in the cat, and the control unit monitors that sensor.

 

Thanks Wally. I did read your article on the vacuum system and found it very informative. That's how I found the timing relay. No real vacuum probs. though. I did have some air pump issues when I did the T/B- W/P a few months ago. Russ suggested removing the pump could result in converter failure. I didn't remove the pump. If the pump isn't pumping properly could that be a cause of overheating?
Would replacing the sensor be the next step? Or, how do you tell if the cat has failed.
I guess simply unplugging the wire from the timing relay is the wrong approach.
By the way. I'm in need of a better service manual than what I have. Got anything?
Appreciate your time.

 

I'm sorry. Did you say Japanese?
A fast, hot, 24 yr. old Asian girl with a bad cat. hmm.
How many 928's went to Japan anyway. I'll find out.

 

Best source of info is the tech info CD set that Jim Morehouse has prepared. A huge amount of tech info (virtually all that is known, in fact), including the workshop manuals, wiring diagrams, traning booklets, tech spec booklets, info by years, tech bulletins, etc., etc.

Jim's email is jim928-at-ptd.net (change -at- to @)

On the later cars, the most common cause for cat overheat is failure of one ignition system.

I think that the first thing to do is to try to see if the cat is really overheating. It probably would be pretty obvious.

 

Ten-Four. And thanks.
I'll be back.

 

I have an 1984 as well. I removed the cat and put in a "Y" pipe from Roger. This also allows you to delete the air pump as well. In NY, after 25 years, there is no more emission testing. Yahoooooo, more power now. Also did the TB and WP last week.