Emissions Maintenance Timer

[madmax]

So I have a very annoying rattle/buzz coming from my dash in my 1988 MJ Sportruck. After investigation I find the  noise is coming from a very curious looking part under the dash which I have now identified as the "Emissions Maintenance Timer". My question is "What the hell is this thing????" and "Can I live without it????". I guess as another issue is whether I can find the part if I simply need to replace it.

 

Thanks for any help!

[yxmj]

Unplug it ....you will live

[gogmorgo]

It's only there to turn on a light every 50,000 miles or so, which reminds you to check your O2 sensor.

You don't need it, but it may not be easy to find another one if some day you decide to restore the truck to show-quality factory spec.

[madmax]

Thanks for the info. I may just remove it and save it. The truck I bought is absolutely bone stock, 77K miles, original paint, etc. (even has the original AMC branded keys) I am a little reluctant to make any serious permanent modifications for that reason.

[Minuit]

Understandable. Its only function is to turn on a warning light, so you won't hurt anything by taking it out.

[cruiser54]

It's designed to trigger an Emissions Light about 82,500 miles to remind you to REPLACE your oxygen sensor. 

[gogmorgo]

Ah, thanks for the correction, Cruiser. I had 80,000 in my head, but couldn't remember if it was miles or km.

[cruiser54]

Ah, thanks for the correction, Cruiser. I had 80,000 in my head, but couldn't remember if it was miles or km.

Actually, it went more by time than miles, but 82,500 was when you were supposed to replace the O2 sensor.

Reason this sticks with me is the light didn't come on at the same time as a major, or any for that matter, service. Customers would be pissed.

[Eagle]

 

Ah, thanks for the correction, Cruiser. I had 80,000 in my head, but couldn't remember if it was miles or km.

Actually, it went more by time than miles, but 82,500 was when you were supposed to replace the O2 sensor.

Reason this sticks with me is the light didn't come on at the same time as a major, or any for that matter, service. Customers would be pissed.

 

And, since the timer was nothing but a timer -- it wasn't a sensor nor was it able to read actual elapsed mileage -- the 82,500 miles was only a vague approximation. The timer sat there, ticking away at a constant rate, whether the engine was idling in traffic, bumbling along at 30 MPH on city streets, or zipping down the highway at 75 MPH. In reality, the O2 sensor might have gone bad long before the light came on, or the light might have come on when the O2 sensor still had a lot of miles left in it.

 

It was one of the dumbest ideas the Jeep engineers ever came up with. Even dumber, the light module wasn't designed to be serviceable -- in addition to replacing the O2 sensor, you were also supposed to replace the timer module. Since then people have figured out how to reset it, and you can find instructions on the Internet, but resetting it was never supported by the factory.

[madmax]

I removed it--a real bear to get to--and tucked the power lead back under the dash. Now I have a nice quiet ride!! The timer is a real Rube Goldberg looking thing, filled with small gears that mesh together.You would think that to save money, the manufacturer would simply have placarded the engine compartment with a notice to replace the O2 sensor at the correct mileage.