1997 Caravan 2.4L. I have replaced the O2 sensor indicated by code P0140 but the check engine light remains with the same code. (all codes were reset). A local auto parts store had a guide that suggested checking the circuit breaker, fuse or relay.
Does anyone know where this might be located. I cannot find one labled for o2 sensor so I am guessing it may be using another or it is undocumented.

 

if there is a fuse relay or breaker for it.. its news to me.. need to check all wiring.. and make sure you replaced the right o2 sensor

and if its the front o2 sensor giving you problems.. might want to make sure the cat isnt plugged up.. that will also trigger the c/e light on that code.. the o2 sensor is just doing its job.. do you smell rotten eggs while driving? lack of power? 'putting' ? all signs of a plugged up cat.

 

It was the rear sensor that was replaced. I've not had bad exhaust smell or lack of power (other than it is a 2.4 litre).
The wiring goes into a hole up into the chasis, so very difficult to follow. There isa rubber grommet that holds the wiring securely in place in the hole which when I removed the old one, there was quite a bit of water which came out.

So if there's not a fuse or relay involved then where should the wiring lead to. The PCM?

 

thats correct..it will go to the pcm.. in a long roundabout way.. those sensors report back to the pcm and the pcm will decide on the rest... i would pull the other o2 sensors and clean em up real good.. then put em back in.. see if it helps.. you might just find a burned up wire on one of them

 

OK Thanks. At least I now know I'm not trying to track down a relay or fuse. I'll replace the other sensor and triple check all connections. Probably won't be until next weekend but I'll let you know what I find out.
Thanks for the advice.

 

Hey all.... Hoping to get some fresh thoughts here. I have been getting this code on my 2007 caravan, I have changed the following:

upstream O2 sensor
downstream O2 sensor
coilpack
plugs
wires
cat
MAP sensor
Throttle position sensor
Fuel filter
fuel pump

also, recent oil and filter change, and seafoam treatment.
After changing the cat, no code for about a week or so, but now it's back

 

^ forgot to mention, the code I am getting is P0420

 

if it was my problem I'd use my scanner and read the data coming from the O2 sensors. if the upstream and down stream readings are identical, then the cat has failed and will set a P0420 code (which I come across a lot on the 2.0 and 2.4 engines)

 

Symptom:
P0420-CATALYTIC EFFICIENCY (BANK 1)
When Monitored and Set Condition:
P0420-CATALYTIC EFFICIENCY (BANK 1)
When Monitored: Engine Run time greater than 90 seconds. Engine Coolant greater than
70°C (158°F) Vehicle speed greater than 20 MPH and less than 55 MPH. Engine Speed
greater than 1216 RPM and less than 1952 RPM.
Set Condition: As catalyst efficiency deteriorates, the switch rate of the downstream O2
sensor approaches that of the upstream O2 sensor. If at any point during the test the
switch ratio reaches a predetermined value a counter is incremented by one. One Trip
Fault.
POSSIBLE CAUSES
GOOD TRIP EQUAL TO ZERO
VISUALLY INSPECT CATALYTIC CONVERTER
EXHAUST LEAK
ENGINE MECHANICAL CONDITION
AGING O2 SENSOR
CATALYTIC CONVERTER
TEST ACTION APPLICABILITY
1 NOTE:Anew rear O2 Sensor along with an aging front O2 Sensor may cause
the DTC to set. Review the repair history of the vehicle before continuing.
NOTE: If an O2 Sensor or Fuel System Lean DTC(s) is set along with the
Catalytic Converter Efficiency DTC, diagnose the O2 Sensor DTC(s) before
continuing.
NOTE: Check for contaminates that may have damaged the O2 Sensor and
Catalytic Converter: contaminated fuel, unapproved silicone, oil and coolant,
repair necessary.
Ignition on, engine not running.
With the DRBIIIt, read DTCs and record the related Freeze Frame data.
Is the Good Trip Counter displayed and equal to zero?

 

Freeze Frame Informationplease note that both O2 sensors are new, as is the catalytic converter. an OBDII scan and freeze frame data gives the following info:Parameter DescriptionValueDTC for which Freeze Frame was StoredP0420Fuel System 1 StatusClosed LoopFuel System 2 StatusNot SupportedCalculated LOAD Value42.35 %Engine Coolant Temp194.00 °FShort Term Fuel Trim - Bank 1-0.78 %Long Term Fuel Trim - Bank 10.78 %Intake Manifold Absolute Pressure15.40 inHgEngine RPM1,469.00 rpmVehicle Speed Sensor44.74 mphIgnition Timing Advance #1 Cylinder40.00 °Intake Air Temperature87.80 °FAbsolute Throttle Position18.04 %




Pending Codes P0420Catalyst Efficiency Below Normal (Bank 1)
Conditions For Setting This Code:
Possible Causes:
Monitor Information:

Diagnostic Information Freeze Frame InformationParameter DescriptionValueDTC for which Freeze Frame was StoredP0420Fuel System 1 StatusClosed LoopFuel System 2 StatusNot SupportedCalculated LOAD Value42.35 %Engine Coolant Temp194.00 °FShort Term Fuel Trim - Bank 1-0.78 %Long Term Fuel Trim - Bank 10.78 %Intake Manifold Absolute Pressure15.40 inHgEngine RPM1,469.00 rpmVehicle Speed Sensor44.74 mphIgnition Timing Advance #1 Cylinder40.00 °Intake Air Temperature87.80 °FAbsolute Throttle Position18.04 %