1985-1998 [Subscribe to Daily Digest] |
 | [Main 9000 Bulletin Board | BBFAQ |
Prev by Date | Next by Date | Post Followup ]
Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
O2 sensor test Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 12 Jul 2002 10:56:21
In Reply to: How to test o2 sensor???, 9k Wrencher, Fri, 12 Jul 2002 01:59:29 Members do not see ads below this line. - Help Keep This Site Online - Signup |
You can test the O2 sensor, up to a point.
The O2 sensor is part of a closed-loop control for the engine, so reading the wrong voltage may not mean the sensor is bad.
Two basic things go wrong with the sensor - it fails to provide the proper output - stuck high (rich) or low (lean), or the response slows down. Of the two, the first is easiest to check.
Connect the positive lead of a good digital voltmeter to the signal lead of the sensor. Most sensors have three leads - the two wires of the same color are the heater, and the signal is the one left. Connect the negative lead of the meter to a good ground. It's important to keep the O2 sensor in the circuit - don't disconnect it to connect up the meter.
Start the car and let it idle. Read the voltage. If everything is all right, no vacuum leaks, the AMM set right, etc, the voltage should vary between about 0.2 volts and 0.9 volts, crossing 0.5 around 1 per second. If you're having engine problems, I doubt you'll see this.
The sensor is probably stuck at one end - 0.2 volts or so (lean), or 0.9 volts or so (rich). You want to know if the sensor will actually move the other way. If it's stuck at 0.9 volts (rich), pull a vacuum line off the intake manifold. The fat one going to the charcoal canister is good, or the hose to the distributor (if your car has one). You want to make a vacuum leak. This will cause a lean condition, and the voltage should drop down from 0.9. If it does, then you know the sensor output moves, and the sensor isn't totally dead. If it stays at 0.9, replace the sensor.
If the sensor is stuck at 0.2 volts or so, it's reading lean. Assuming you've scoured the car for vacuum leaks, what you want to do is make the engine run rich. Take the vacuum hose from the intake manifold to the FPR, pop it off the FPR end, and plug it. This will make the FPR think you're at boost, and will enrich the mixture. The voltage on the O2 sensor should come up off the 0.2 volt stop. If the sensor is stuck at 0.0 or 0.2 volts, you either have a really big vacuum leak somewhere else, or the sensor is bad.
If the sensor response slows down, it can affect drivability of the engine. No real good way to test for that. I haven't been reading your posts, but if you've got a big engine problem, a slow sensor probably won't be the problem.
Good luck!
posted by 140.157.4...
, Fri, 12 Jul 2002 10:56:21 <-- Viewing This Message
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
