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Leo, Auto Service Technician
Category: Dodge
Satisfied Customers: 770
Experience:  2005 Dodge ASE master technician of the year
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Grand Caravan: P0172..within 20..20 miles..start cycles bank 1 to rich

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Code P0172 01 Grand Caravan keeps returning within 20 miles no matter how many or how few start cycles bank 1 to rich. What is your suggestion to find problem?

Hi, and welcome to Just Answer!

The code indicates that the oxygen sensor is sending a rich (or to be more technically correct a low oxygen) signal to the engine controller that it's unable to compensate for by adjusting fuel delivery.

Any problem that causes the car to be rich can trip this code.

  • failed oxygen sensor - if the sensor fails and sends back a bad reading to the controller (in this case something greater than .5 volts) then this code will set. One of the more common reasons.
  • high fuel pressure - if the fuel pressure is excessively high it will skew the system towards rich, the computer detects this and you'll get the code
  • purge solenoid - if the purge solenoid fails, it can allow excess fuel vapors to be drawn in when the computer isn't requesting it.. possible but unlikely to occur without some other codes relating to the purge or evaporative emissions system
  • bad map sensor - if the sensor is out of calibration it'll throw the fuel delivery calculations off.. unlikely without other DTC's but possible
  • throttle position sensor - pretty much the same story as the map sensor.

Without access to a scan tool to display live data and verify sensor readings, the best place to start in my opinion would be the oxygen sensor itself. They are really a tune-up part in my opinion and should be replaced on a regular basis anyway, just to maintain engine performance and economy. I do not however care for the 'universal' wire it yourself type that many parts stores sell, often times they cause more trouble than they are worth..

The sensor in question is of course the one that's more harder to get to, it's the one located in the exhaust manifold, just before the flange for the catalytic converter.

I hope this helps, if you need more information, or have more questions, please don't hesitate to reply back and ask!


Leo and 7 other Dodge Specialists are ready to help you
Customer: replied 9 years ago.
Reply to Leo's Post: Hi,

Thank you for your advice. I do have access to a scan tool to look at live data. Both upstream o2 are producing readings as they should varying greatly within the set values. Both downstream are relatively steady. Would you still think that this is an o2 problem

I'm confused now.... we are talking about a 3.8 caravan right? It should only have one upstream and one downstream O2 sensor. If your scan tool is showing 4, are you sure it's not displaying them backwards? I'd unplug the downstream and see what value changes..

What are your current long and short term adaptives?

Can you get the freeze frame info?


Customer: replied 9 years ago.
Reply to Leo's Post: Hi,
Sorry, I got the info from a ford tech it was his scan tool there are only 2 one on the back manifold pre-cat and 1 post cat. I made the assumption there were 4. I am going to accept your answer and get you paid. I think that will fix the problem. If not I will ask again or email you accordingly. Sixty five bucks for a O2 is cheap enough to find out.