My friend has a 2000 XKR (97K) and has had a constant problem for several years with p0171 and 0174 and of course going into restricted performance.
If you want to know more on the history your can look at this post (https://www.jaguarforums.com/forum/x...6/#post1618134).


Most recently he was following me on the highway and according to the freeze frame he was running at 73mph with 2660 rpm and threw a cel. We checked it and it was a p0171 and p0171-with short terms at +25 and +24.2 and long terms at +12 and +11.8. However he did NOT get a restricted performance! He used the car 2 days after that and I saw on the scanner beyond the original p0171 and p0174, some pending of the same. At no time did he go into RP. The CEL has now gone away on it's own, but he still cannot get the ccm and exap monitors to set. (My opinion is that he has a small leak below the throttle body and likely either the egr bolts or the many vacuum connections and that metal bellow is a prime suspect).


My main questions is simple- what does it mean that you throw a p0171 and p0174 and NOT go into restricted performance?????


He has once on startup, thrown a CEL and checked it and found a p1642, but that is the first and only one, never to appear again. I think it was just an anomaly and not relevant. I stand to be corrected.


Thanks


Tom in Dallas/Plano

 

I guess it would be possible for a code to appear and go away before lasting long enough to trigger an RP light. The 02 sensors would detect a lean condition pretty rapidly as they're situated directly after the exhaust headers in the cats. I don't recall seeing anywhere any mention of the time it might take for such a condition to trigger restricted performance.

Since air leaks don't appear and disappear I'd think it might have been caused by some sort of hiccough in the fuel delivery (injector pulse interrupted or dirty filter??). Something like that could cause a momentary lean that might not last long enough to trigger RP.

Just a shot in the dark

 

Thanks. I appreciate that, but we have been chasing the 71 and 74 for 2 years (The owner is really more in tune with 1990 type cars than the newer ODBII systems). It has varied from happening every-time- to be intermittent. Even normal fuel trims are off- for example when cruising at any speed, be it 10, 20, 60, 70 mile an hour they run at +12 LT and if you just step on the accelerator being it from a dead stop and go slowly to 10 miles an hour the short terms immediately spike to +25 on both sides. Same works on any acceleration at any speed.

I just cannot find anything to talk about getting those codes which take a 2 trip mil cycles to initiate a CEL that do not throw the car into restricted.

Thanks

Tom in Dallas/Plano

 

Back in mid-February my wife's 2006 XK8 threw codes P0171 and P0174. I would clear the codes, drive the car, and both codes would immediately return. I cleaned the mass air flow sensor and changed the spark plugs (they were past due at about 108,000 miles) as my trusted indie shop suggested but neither job cleared the codes. I took the car to them in late February for diagnostics. They ran a smoke test and determined that both VVT solenoid O-ring seals were leaking air (I had replaced them with relatively inexpensive new O-ring seals I ordered online a couple of years prior). New better-quality OEM VVT solenoid O-ring seals immediately cured the problem. Both codes were finally cleared and neither has returned....

 

I've dealt with these codes in the past. I recall neither a P0171 or P0174 will set any other driver notifications other than the CEL - so to get a restricted performance there has to be something else. Also, I recall, each one needed 2 consecutive trips for the code to be set where trip is defined as XXX ( I don't remember). Somewhere I had the factory specs on every code, what it took to set them, whether there was an associated Amber, or Red warning as well; how quickly they self cleared (when fixed) but I suspect it is on an older laptop I either got rid of or in the basement.

Check these 2 things for those codes: MAF, and more probably, the bypass valve actuator. It has a diaphragm inside which allows air to leak in, hence the lean codes for both banks. That was my problem and it did take me a while to track down. I was able to install without touching the inter coolers, and only loosening the TB so I could push it back about 1 inch. It is possible. Also, any other air leak could cause (like cracks on bottom on intake tube or split vacuum lines).

 

To be honest, I cannot find anyone who has a CEL due to 0171 and 0174 that did not have a RP. MAF is running fine and allowing the airflow as pointed out on Gus's site and has been cleaned. Attached are the standard ODBII read of the codes.

Where the devil is the bypass valve actuator- unless you are talking about the one under the wheel wheel on the front left of the car (we have replaced that)?

Update:

I went and looked and I know now what you are speaking about and where it is.

Thanks

Tom in Plano/Dallas

 

Attached is for 2003 XK8's and XKR's (4.2 engine), if it helps.

 

Thanks, but I have all of that and attached the one for 2000 in the previous post. I have not seen a CEL though for a combined p0171 and p0174 that did NOT result in RP and that is what the info in both attachments indicate would happen. Previously on the same car when we had the same codes it always resulted in RP. So that leads me to think there is another problem that is not showing completely, perhaps due to the incomplete monitors, but they were not complete before- so I am still left with the question.

Thoughts

Tom in Dallas

 

Driver Warnings:
N = None
R = RED MIL (warning lamp) plus Message Center message
A = AMBER MIL (warning lamp) plus Message Center message
C = Charge indicator

When I had my issue I was surprised as well why I didn't have a restricted performance for both lean banks...after looking into it, I realized I'm not suppose to because of this chart. At least that is what I recall, it was a while ago. The only thing memorable to me were those 2 lean bank codes, no restricted performance, and the bypass actuator fix.
I suspect if you want to check if your car can get Restricted Performance to maybe unplug the MAF, or TPS.

 

Tom, I have a '99 XK8 (I realize not an R) and I also have a P0171 code and it does throw an RP. BUT, I also have a cam sensor code and a P300 series code indicating not only an air leak but also a misfire AND because of the cam sensor problem an erroneous fueling problem on the left bank. So I have a possible air leak affecting the right bank, a fueling problem affecting the left bank because of cam timing, and a random misfire on the left bank.

Combined they triggered an RP. Like you I figured the P0171 or a P0300 series code would trigger the RP.

But I was wrong.

In running a search within the 1999 XK8/XKR factory service manual for all instances of P0300, P0171-P0175, and P1341 codes the ONLY one of those that will trigger an RP ON THEIR OWN is the P300 series.

The P0171-P0175 and the P1340 & 41 codes DO NOT trigger an RP by themselves.

It may perhaps be different in 2000 and later models (which I doubt highly) but at least in 1999 they did not regardless of being SC'd or not.