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2003 Caravan SE with 164,000 km on a 3.3 litre. What would be the most common causes for tripping a P0171 (system too lean) code? I haven't been able to locate any holes in the air intake system. Put in a new air filter while I had it apart and managed to clear the code with a friends Elm327 OBD2 interface. The fix lasted through a half dozen cycles, then tripped again 2 days later. I haven't noticed any loss in performance .... just like to fix little problems before they turn major.
 

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Most likely a vacuum leak or O2 sensor problem. I would listen and check for vacuum leaks using propane or brake kleen first.
 

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Just to note, there is no Mass Air Flow sensor on the 3.3, so you can rule that out as being dirty. So it's either a vacuum leak or a faulty O2 sensor that died in the lean position.
 

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Just to note, there is no Mass Air Flow sensor on the 3.3, so you can rule that out as being dirty.
Yup that's correct but it does have a Manifold Absolute Pressure or MAP sensor that serves the same purpose using a slightly different method. You can rule the MAP sensor back in as a possibility. As we all know the MAP sensor can generate erroneous data and not throw it's own fault code.
 

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I typically rule out the MAP sensor if he's getting no driveability issues. They usually cause some rough running, if no running at all, and random stalling.
 

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Discussion Starter #7
Thanks for the replies, light is still on. Have not noticed any driveability issues, rough running, or stalling. It does seem to take awhile longer to warm up lately (this happens every winter). There is an air intake temperature sensor inside the hose connecting the air filter housing and throttle body. If this was contaminated, say sending out a reading that was too high to the CPM, then wouldn't this register as running lean on start up with less of an impact the closer the engine gets to operating temperature?

No, engine does not have a MAF sensor. I've had issues with MAP sensors on other vehicles ... mostly the problems were related to excessive carbon build up. Symptoms came and went as the carbon flakes fell off. Another thing this engine doesn't appear to have is a PVC valve ... although Blue Line offers a part number for it.

I've done the propane probe thing without too much success. I don't think I was getting enough volume through the hose because I ended up sticking it right in the air intake without getting any change in rpm. Will be trying again tomorrow with a few modifications. Aside from a vacuum leak, does anyone know what kind of voltage readings I should be getting for the upper/lower sensors? Is it worth it to change both of them out at the same time, or, just the upper?
 

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I have a 2002 T&C and have had the same issue. Started with code p0169. Changed the PVC valve, replaced the breather hose, change the O2 sensor (upstream), cleaned the MAP sensor and recently changed the fuel filter. Now I am getting code p0171. Cleared it and it came on again in about 10 miles.
Do I change the MAP sensor, or change the fuel filter? What is left?
 

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a vaccum leak would cause the car to run rich since its sucking in more air. I would start of by replacing your fuel filter and checking your air filter and even cleaning out the throttle body. do all this with the battery disconnected. before reconnecting the battery touch the positive lead and the negative lead tighter (make sure ether ground or positive is disconnected before doing this) hold them toghter for about 5 secs. this will remove all memory on the pcm cause the pcm to relearn the long term and short term fuel trims.
 

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Throttle body components or coil pack

If your idle air control valve (IACV), which is in the throttle body, is not closing when the throttle is opened (change in signal (voltage) from the throttle position sensor)---it is like having a massive vacuum leak. The engine will run rich, the manifold air pressure will rise (Less vacuum), which in turn effects spark timing. The engine will run like crap. Preignition, detonation, stalling. My van was drive-able as long as I kept my foot out of it. Coil packs are also effected by years of heat. They break down and start doing weird things too. Since you already changed the MAP sensor, I'd change the TPS and IACV. Remember to remove the negative battery cable to reset the computer. If that doesn't fix it, I'd change the coil pack
 

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If your idle air control valve (IACV), which is in the throttle body, is not closing when the throttle is opened (change in signal (voltage) from the throttle position sensor)---it is like having a massive vacuum leak. The engine will run rich, the manifold air pressure will rise (Less vacuum), which in turn effects spark timing. The engine will run like crap. Preignition, detonation, stalling. My van was drive-able as long as I kept my foot out of it. Coil packs are also effected by years of heat. They break down and start doing weird things too. Since you already changed the MAP sensor, I'd change the TPS and IACV. Remember to remove the negative battery cable to reset the computer. If that doesn't fix it, I'd change the coil pack
It's easy to miss the dates. You're answering a year and a half old post.
 

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Also I might add, none of the members with this code on this thread were having any driveability issues at all.
 

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This is common for a Newbie when searching the threads for interesting posts, have done it quite a few times myself on a new forum:)
 

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geese just love the outcome the fix result that wasnt posted
having same issue, mostly notably is mpg is down from 21ish to 14.5mpg
im thinking 02 sensor van have 234,000 miles i havent changed them since i bought at about 100k miles
 

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Yes, this is an old thread, but I'm resurrecting in hopes that someone can help. I have the same code but no real issues. I posted another thread with the one issue I have but I'm not sure they're related.

I replaced the MAP about two years ago. in the last 3 months I've replaced spark plugs, wires, coil, TPS, cleaned TB, fuel filter, Emissions purge valve, emissions valve down by emissions canister, upstream o2, I've opened the intake manifold and confirmed the gasket is good. I've found some cracked vacuum lines and replaced them.

All I have left is the down stream o2 and... ?
 
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