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What P0141 actually means:
Posted by Jeff Cullen (more from Jeff Cullen) on Thu, 9 Feb 2012 08:29:10
In Reply to: Load sensitive, stumbling above 2000 rpm, P0141 code, leapfrog, Wed, 8 Feb 2012 14:53:54
is that the pre-heater in the 2nd O2 sensor (behind the cat) is dead. O2 sensors don't work until they're running hot enough to get a read on things, so the ECU runs in "open loop" mode until it starts getting a signal, when it can switch to "closed loop" mode where fuel consumption and emissions are optimized.

One-wire O2 sensors (which we haven't seen on Saabs since the 8-valve 900s) are grounded by their contact with the exhaust component into which they're screwed, and send their signal on the black wire.

Then we had three-wire O2 sensors which add two white wires into the mix--these carry 12V to a pre-heater which brings the O2 sensor online faster.

Finally, four-wire O2 sensors add a grey wire which is signal ground.

P0141 indicates that we are not seeing the correct resistance from the preheater circuit (i.e. across the white wires). Now, I don't remember what this is, but 4 ohms seems to stick out in my mind. Grab a multimeter and compare the resistance of the heater circuit in both your O2 sensors. If those values are different, replace the offending sensor. The rear O2 sensor behind the cat really needs the heater be working because it's so far from the action that it isn't easy for it to come up to temperature.

Good news though--you don't have to spend $250+ on a replacement -- go to any local parts store that sells Bosch O2 sensors and ask for the generic splice-in 4-wire jobbie. Make sure it's Bosch. The new sensor will come with four butt splices and some heat shrink tubing. Simply snip the wires off of your old O2 sensor, slip the heat shrink tubing over the wiring, join the four wires using the butt splices, and use a lighter to close the heat shrink tubing around the butt splices to keep things clean and dry.

The old sensors can be a bear to unscrew if they've been in there a long time -- I like to use the box end of a 22mm wrench after I've cut the wires off the dead sensor.

I'll be surprised if this has anything to do with your stumbling above 2000rpm... but if it were my car, I'd fix this anyway.

Best of luck!
--Jeff
'85 900 SPG
'89 900 SPG
former:
'93 9000 Aero
'93 9000 CSE
various other 900s...

posted by 24.84.216...
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