catalyst efficiency low

[soopersec]

Here is my question - we had a machine put on the vehicle because the check engine light was coming on. When we did, it came up catalyst efficiency low. On a 1998 chevy s-10 pick-up 4x2 what does this mean? Is it the catalytic convertor?

[CivicSpoon]

Try the Chevy forum. But yes, most likely you have a bad cat

[91civichatch2571]

Yea, most likely you need a new cat. If you have access to one, hook up a scan tool to your truck and look at the actual waveforms of both of your O2 sensors. The one before the cat should go, up down up down up.... very quickly. The other (the one after the cat) should be pretty steady and when it does move up or down, it should do it much smoother and not move nearly as much as the primary o2. If they both look like the first one with the constant up down, a new cat is needed. Or you could hollow out your cat and buy and o2 simulator. unless you live in cali or the tri-state area that is.