Question about 2002 Jaguar X-Type

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Xtype 3.0. 50k miles. get constant PO171 and PO174, cruise unavailable. New fuel filter. Flushed injectors. tested for vacuum leaks at MAF and TB. Seems to be triggered by moisture, not sure where to look next. Can run fine for long periods, then bam, Max engine speed reduced... feather the throttle a few times, pops check engine, clears and then runs fine. Always PO171 and 174. Any ideas?

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P0171 and P0174 are both lean fuel mixture codes, one is cylinder bank one and the other is cylinder bank two. This means means you have a common lean fuel condition for the engine when both cylinder banks set this code, this is NOT and indication the O2 sensors are defective. here is a list of the possible causes, each must be checked, it requires special tools that include live data scanner tool and fuel pressure testing equipment, with these code i do not advise guessing, the dealer should get involved in this or a trusted outside shop than has Jaguar testing equipment.
Common Problems:

Common Misdiagnosis:

The Basics:

Combustion engines operate by burning an air/fuel mixture of about 14.7/1 (14.7 parts air/1 part fuel). When the air ratio goes above 14.7 parts, this is called a “lean” mixture, and if the air drops below 14.7 parts it is called a “rich” mixture.

Lean Mixture = Too much air, not enough fuel
Rich Mixture = Too much fuel, not enough air

Posted on Feb 02, 2010


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I have several codes in my 99 Chevy S-10, po171, po174, po303, p1509. could there bo a common problem/

They are related mostly. All have to do with air intake. 170 codes are both sides running lean, to much air. 303 is a #3 misfire, could be a vacuum leak around the plenum. you replaced the spider. Could be the injector not seated right(smell for gas in the oil/dipstick), also could be a bad wire or spark plug. 1509 is an electrical problem with the idle air control motor. Check the plug for corrosion. Also wires usually break a round the plug. This also could be the problems with too much air.

Nov 08, 2014 | Cars & Trucks

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PO174 AND PO171\

code p 0171 refers to system too lean bank1===causes ---intake /exhaust leaks--AIR system---MAF/VAF sensors --fuel pressure/pump--injector/S=== HO2S
code p 0174 refers to system too lean bank 2====causes intake /exhaust leak---fuel pressure/pump---injector/s---AIR system---hose connection/s
the fuel pressure is adequate
The HO2S is the heated oxygen sensor in the exhaust manifold /pipe before the cat converter
( is responsible for the fuel ratio settings )
you may have to pull the injectors to have them cleaned and tested
the maf/vaf sensor may have to be replaced as well

Apr 11, 2017 | 2004 Cadillac SRX

1 Answer


please go to : FOR MORE INFO, good-day!

Apr 17, 2014 | 2004 Cadillac SRX

1 Answer

I have a 2000 Cadillac Deville with 180k miles. I've been getting P0171 and a P0174 code. Yet there is no vacuum leaks. I replaced the MAF and still its idles rough once it heats up. Any suggestions?

Have you not Googled the Codes PO171 & PO174
to learn the problem ?

I would suspect you never changed the front O2 Sensors
at 100,000 miles & they both have now failed

The MAF shouldn't have been the issue

You may also have converters that are worn out
with a 14 year old vehicle

Are you changing Spark Plugs every 3 years ?

A rich fuel issue will drive the O2 lean also
Need to look at Fuel Trim on scan tool & other data

Aug 22, 2013 | Cadillac DeVille Cars & Trucks

3 Answers

2001 ford focus had the spark plugs and wire change. Has a code po171.. ran good for two days. The spark plugs are blacker than acs of spades which is running rich. Don't know what to do next. To me its...

PO171-System to Lean (Bank 1)

Air filter cover tight?
All intake ducting tight?
Clean MAF Sensor.--CRC MAF Cleaner
Fuel Pressure Regulator?
EVAP Purge Valve-stuck open?
Vacuum leaks?
EGR System-issues?

Seems your getting a lean O2 Code,because it is trying to correct for a rich condition,as you said.

Is the Throttle Position Sensor-original?

Work on what is driving it rich,my list is a possible.

May 19, 2010 | 2001 Ford Focus

3 Answers

My 98 f150 has p0171 and p0174 codes, i just had my manifolds change, new egr and dpse sensor.. I spent a lot of money on it and it keep sending out new codes... it been in the ford garage for 4 out of 8...

That could be a bad MAF sensor, check to see if its dirty. That could also be a engine vacuum leak check to see if you have a sucking air sound. If its a dirty MAF you can spray it with electronics cleaner. If you don't find any vacuum leaks and the MAF isn't dirty/ bad then check for restricted fuel filter, weak fuel pump, or dirty injectors. Start with trying to clean the MAF and check for vacuum leaks.

Apr 14, 2010 | 1998 Ford F150 Regular Cab

3 Answers

P0171, P0174

po171 fuel injection system to lean bank 1 po174 same thing but bank 2 that could be the oxygen sensors

Apr 04, 2010 | 1997 GMC Jimmy

1 Answer

My ford truck failed the smog test because bank 1 and 2 are to lean ( p0171 & p0174 )

possible solutions are, a dirty maf sensor. remove manifold air flow sensor and clean it with maf sensor cleaner. you can buy a can at any auto parts store to clean, take off and clean maf sensor, do not touch inside of sensor it is very fragil. when cleaning sensor be sure it is dry before installing it back on vehicle. also check for a vacuum hose leak downstream of maf sensor.make sure air filter is clean. this usually takes care of the problem. po171 and po174 are the same. you can use electrical cleaner to clean sensor also. also check for a dirty fuel filter and fuel pressure, if needbe.

Feb 11, 2010 | 1998 Ford Taurus

2 Answers

2002 Chevy Van with a 3400 code po171 too lean how to fix

Code PO171- Lean mix of Bank 1.
Code PO174- Lean mix of Bank 2.

Most of the time a P0171 and P0174 is caused by either a vacuum leak--more than likely the PCV hose and valve or a dirty or defective Mass Airflow (MAF)sensor. Low fuel pressure can also cause this condition. The PCV hose is located on bank one but can affect both sides because the other end is located on the back of the upper intake manifold. Usually they deteriorate and get a hole in it.

Clean the the MAF sensor with MAF cleaner, which you can pick up at any Auto parts store and also pick up a bottle of fuel injector cleaner. Good luck and hope this helps.

Nov 16, 2009 | 2002 Chevrolet Venture Passanger

1 Answer


Here are the possible causes for the PO171 and PO174 codes:

  • Base engine mechanical problem affecting one or more cylinders
  • Check for air leaks after the MAF sensor
  • Check for air leaks in the Air Induction system (e.g., in the intake manifold)
  • Check for air leaks in the EGR system and in its related hoses and/or valve
  • Check for air leaks in the PCV system and in its related hoses and/or valve
  • Fuel control sensor is out of calibration (e.g., ECT, IAT or MAP)
  • Fuel delivery system supplying too little fuel during cruise or idle periods (e.g., faulty fuel pump or dirty, restricted fuel filter)
  • Fuel injector (one or more) dirty or pressure regulator has failed
  • HO2S has failed (it may be contaminated with fuel, silicone or water)
  • Vehicle driven low on fuel or until it ran completely out of fuel

Please let me know if this information is helpful. Positive feedback is appreciated. Thank You!

Mar 20, 2009 | 2004 Suzuki Verona

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