Allpar Forums banner
1 - 3 of 3 Posts

·
Registered
Joined
·
979 Posts
Discussion Starter · #1 ·
1995 Intrepid 3.3l - has two O2 sensors - one in each exhaust manifold on each side - car is throwing a code 21 02 sensor error with Check engine light coming on sometimes (not consistently ... yet). The code applies equally to L and R sensor - how can I tell which one is on the fritz? I dont have an OBD1 code reader - code reader connector is different than my OBD 2 and I don't think this car is ODB2...
 

·
Registered
Joined
·
979 Posts
Discussion Starter · #3 ·
Thanks - that helps - still intermittent so I'll watch it for a while - I have had these clear on their own before (carbon on the sensor?).
 

·
Registered
Joined
·
979 Posts
Discussion Starter · #4 ·
Well last last week it got to the point where the Check Eng light was on every trip. So I bought a sensor and went at it yesterday.
In case anyone else needs to diagnose one in the future:
Heaters in both sensors checked out - about 8 ohms - just over the spec of 5-7 ohms in the FSM. So I tried an analog voltmeter on the sensor signal - could not really read anything. So I got out the (rarely used) oscilloscope to see what that would show me. Hooked up a trace on one sensor then the other - both looked to be varying between about 0.2 and 0.8V as Crown indicated. It was only when I brought up traces on both sensors together on the scope (one on Ch1 and the other on Ch2) - then you could see - the right one showed a very regular pattern up and down between those voltages - almost sinusoidal - the left one was very irregular - going up and down almost randomly - and sometimes staying at the top or bottom of the trace for maybe 100ms - so I figured replace the left one which I did. I was surprised how easily it came out after 18 years in there (pretty sure it was original) - easily came out with an open end wrench. Last night when I went out to my hockey game - no check engine light - so that seems to have been it.
 
1 - 3 of 3 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top