Please advise - S-Type R, 2002, true 80,000 miles
Recently getting Restricted Performance Yellow Warning.

But intermittent - only came on after 10 miles or so.

Ran diagnostics - I found P0171 - "System too lean - Bank 1"

Have read the several comments here, including - "The MAF (Mass Air Flow) Sensor is dirty or faulty"

Tried cleaning the MAF sensor with the recommended cleaner - but problem remained

So I bought a replacement MAF sensor as my percentage golf shot.

Thought all was OK - but the fault light just came back on after 30 minutes in town driving

Appears to be intermittent -

What do you guys recommend I look at now please?

D
**P.S. I have had P0057 - "HO2S Heater Control Circuit Low - Bank 2 Sensor 2" for some time - but after reading posts here I didn't worry too much.

 

Start with correct available voltage. Use a voltmeter and check the battery voltage across the terminals with the ignition in the OFF position. There should be a minimum of 12.6 volts available for all modules to function correctly.

 

Fix the cause of the P0057.

After, let them relearn and see what the fuel trims are at idle (hot engine).

P0171 is unlikely to be MAF unless you also have P0174 (think why!) and even then you typically get RICH not lean codes...

But ffs fix the P0057. You're hamstringing the engine now, and doing the same to diagnosis.

 

The peak MAF reading should exceed forty times the engine's displacement. Read https://gearsmagazine.com/magazine/m...y%20acceptable.

 

Im think massive vacuum leak. Do a smoke test. Look for leaky O-rings or broken vacuum lines or leaky gasket tighten it oil cap

 

Battery - bizarre Only 12.4v
And I charged overnight only a week ago with an Intelligent Pulse Charger
Am recharging now.
Battery - recommended for car - only 4 years old.

 

Four years old, is reaching the replacement age for an auto battery...

 

Good point
Maybe the battery is going - but down here in the SE Cote d'Azur of France, the weather is very mild and in theory less strain on the battery

The original lasted for 18+ years.

 

Restricted performance doesn't usually throw any codes. Most likely suspect is potentiometer on the throttle body.

 

🤦‍♂️ i thought you knew better than this

rp is generic message for like a dozen different faults and they have different failsafe modes.​​​​​​ lean feedback loop limits you to 3k until ltft goes under 18.5

 

S-Type ones tend to go much longer if not maltreated (7+ years). I think the longest reported here was 14.

 

I am aware of some OE batteries that have lasted for very extended periods, given a mild climate and non-maltreatment... I have heard that the current crop of auto batteries are not as long lived as the originals, given changes in plate design/materials.

At four years old, the battery should always be suspect, until proven otherwise.

 

Thanks - I'm sure you are right.

After overnight charge with Intelligent pulse charger it was only showing 12.6 volts.

Originally it showed 14.6v and held it for some time.

So I'll get a good new battery.

 

Thanks. In my situation - until the Restricted Performance warning shows, there is no code shown by the diagnostics, only after.

 

I think for an S-Type you're not right about that.

It has two and they must agree closely or a code is flagged. That's not happening here.