While I understand, sort of, what the above codes mean and some of the solutions I have read make sense. What is intersting is that the code is registered after hwy drive of 30 miles. Then after two days of city driving, the code goes away. If amyone can provide input on that I would appreciate as why the code appears only after hwy driving.

Thanks.

 

Year/ model/ engine displacement

 

The car is 2003 Van Dan Plus. V8, and has about 63K miles on it.

 

Sounds a bit like the opposite of an air leak? Dirty MAF maybe? Or a "lazy" O2 sensor? Blocked fuel filter? (Has it been changed? It's due about 60K miles.)

Cleaning the MAF is easy (DIY - do a few searches). Fuel filter's easy (more searches). Don't change an O2 based on my guess!

Have you any misfires logged?

 

P0174 is System Too Lean Bank 'B'. This will almost certainly be an air leak somewhere in Bank B from where the inlet manifold splits into 2 to feed Bank 'A' and 'B', or possibly a leak in the exhaust manifold / catalyst or where the O2 sensors are fitted into the exhaust. Cleaning the MAF is unlikely to make a difference, as if this is the problem you'll either get a lean code for both banks (P0171 and P0174) or a MAF sensor code (P0101). If the O2 sensor is a fault you'll get an O2 sensor code for Bank B, so don't chance an expensive change of this!
A blocked fuel filter won't only give this code (again it'll affect both banks), ditto the air filter.

As regards to only showing up on highway driving, the leak may only be small and only evident at a higher under bonnet temperature.

Good luck searching for the leak!

 

Hi. JagtechOhio and jagv8,

THanks very much fo rthe input. Very much appreciate this assistance.

I added some fuel additive by Techron and drove the cars at high speed between 70-80 MPH (averaging 50 MPH). for about 70 miles rt, then followed it with another 55 MPH for 20 minutes. The check engine light has not come on yet. Either the car has given up on me (lol) or a temporary symptom have gone away. Any thoughts other than what you have suggested? This is driving me crazy. My car is due for a smog test, and I am not if this will thorw off the test or not.

To answer some fo the quesitons asked by jagv8:
1. THe fuel filter was changed about 15K mile ago because fuel pump went bad (done by the dealer)
2.No mis-fire at all. Actually the car drove as if it was from the factory yesterday. Mileage is great too.


Again, thanks.

Abe

 

You CAN get either p0171 OR p0174 together OR by themselves because of a defective air flow meter! I just fixed one today. A p0174, with a faulty air flow meter.

 

Dude, I was biting my tongue 'cause I thought that was going to start a technical argument which would wind up over my head...but I was pretty sure that a dirty MAFS could set only one bank's code. I have cleaned them on cars before and never saw the fault again.

It probably only happens when the MAFS signal is right on the knife edge of setting the DTC's, but it is not implausable and I agree that it happens in practice even if the logic is debateable. And cleaning a MAFS is often ineffective, just in case anyone reading this is wondering. Replacing them is more often then not the better way to go for reliability.

 

Thanks again, all of you, for your input. See next post for more details

 

Thanks again, all of you folks, for the input. I will start to take one item of the suggestionat a time and find the cure. In the meantime, here is the first read off the system (using Auto Tap) that finally got in text format for this post. If there is anything that you notice to narrow down the issue, please advise.
Confirmed Diagnostic Trouble Codes:
Code: Description:
P0171 Fuel Trim System Lean Bank 1
P0174 Fuel Trim System Lean Bank 2
Possible Diagnostic Trouble Codes:
Code: Description:
P1111 IAT Circuit Intermittent High Voltage
--------: EMISSION TEST STATUS :--------
Emission Status: <SELECT DATE>
Vehicle Model Year: <SELECT>
OBD Compliant: Yes
Misfire Monitoring: Complete
Heated Catalyst Monitoring: NotSupported
Comprehensive Component Monitoring: Complete
Catalyst Monitoring: Complete
Fuel System Monitoring: Complete
Evaporative System Monitoring: Complete
Secondary Air System Monitoring: NotSupported
EGR System Monitoring: NotSupported
Oxygen Sensor Monitoring: Complete
Oxygen Sensor Heater Monitoring: Complete
A/C System Refrigerant Monitoring: NotSupported
--------: FREEZE FRAME DATA :--------
Generated by DTC code: P0174
Fuel System Status Bank 1: CL-1
Calculated Engine Load: 40.4 %
Engine Coolant Temperature: 194 °F
Short Term Fuel Trim Bank 1: 10.2 %
Long Term Fuel Trim Bank 1: 19.5 %
Short Term Fuel Trim Bank 2: 10.2 %
Long Term Fuel Trim Bank 2: 19.5 %
Engine Speed: 2095 RPM
Intake Air Temperature: 73 °F
Mass Air Flow Rate: 4.373 lb/min

 

That shows an insignificant difference between the mixture that both banks are burning (the figures are identical), meaning that a vacuum leak is not likely to be the cause. It certainly couldn't be a significant leak. It also indicates that none of the four oxygen sensors is sending a bogus signal. My suspicions remain unchanged.

 

Reading the codes always gives a wealth of detail, both Bank A and Bank B are fairly well in balance in terms of fuel trim, if there is an air leak, it will be after the MAF and before the split into Bank A and B. Check the zip tubes for splits or poorly fitting connections.

As a point of curiosity, there is also a code for IAT (Inlet Air Temperature). This sensor is co-located with the MAF (Take the MAF out of the inlet manifold and it's the black bulb like sensor visible at the end). This may mean there is a poor connection at the MAF harness. If there is a high resistance on this connection, there may be a reduced voltage coming from the MAF, which means it will under report the amount of air flowing into the engine, which could cause lean codes.

I'd be very interested in the long and short term fuel trims before and after MAF cleaning, (and how much dirt is removed !) if this fixes the problem.

 

That freeze frame would secure it for me. Air flow for sure. Notice the RPM and Calc. load. I think he was in high gear cruising say between 50-60 mph at the time of the frame capture. This is a classic Jaguar "under load" lean condition. A guess at the speed, but an educated one. Flight recorder would tell the whole story.

I don't clear the code until I see the trim drop significantly with lean conditions such as this one. When it does finally drop into line, I clear the code.

 

Code P1111 is simply the drive cycle not complete for an XJ8. I do not know why, but many scanners apparently report that as the IAT fault. After the drive cycle completes, P-1111 changes to P-1000.

 

Hi. All,
Thanks very much for your input and suggestion. I am very impressed by it. I am away for a week. Upon return I will start to work on the suggestion and will report. In the meanitme, if there anything else that comes to mind, please advise.
Again, thankis

 

I GUESS ILL CHIME IN... 1ST THOSE FUEL TRIMS ARE OUT OF WAC. 6%+/- IS ACCEPTABLE. AND AS POBOY POINTED OUT TOO. LONG TERM FUEL TRIM IS ADDING A HELL OF ALOT OF FUEL. ANOTHER ISSUE IS IF YOU DONT CLEAR LONG TERM FUEL TRIMS AFTER A REPAIR OR SUSPECTED REPAIR. MANY TIMES YOU END UP WITH REOCCURING FAULTS SET BEFORE LONG TERM SELF ADJUSTS!!! DO A BATTERY HARD REBOOT TO CLEAR. AND I WOULD REPLACE THE MAFS, BARRING NO VACUUM LEAKS AT INTAKE TUBE CONNECTIONS..ETC ITS A COMMON PROBLEM. i HAVE SEVERAL TESTORS AND A NEW V8 MAFS FOR $60 IF YOU WANT IT

 

based on the short and long term data both banks are at fault,p0171 is about to flag good chance its the maf you can clean them it may buy you some time,another thing to check is the is the o ring that seals the line for the brake booster its on the right side just bellow the throttle

 

Thanks Tech4Jag, much appreciate your response. Actually for some reason I failed to understand. The check engine light has gone away, the car seems to run just fine. But what you mentioned about the brake booster is intersting. I will have someone look at that too.
The car is due for a smog test. Hopefully that will also shine some light on the issue. But my mechanic has asked to stay put until the check engine light comes back on and to note what condition that light comes on. THen he will look into it more. He has mentioned it several times that as long as the car is running fine, these faults can recycle and until we know that condition it shows up, we would be wasting time. Hope he is right.
Abe

 

Hi. All,
As promised a few weeks back that I was going to try and recreate the condition where my car turn up the amber check engine light. Well, today I was able to. The conditions were a round trip drive of about 80 mile with HWY speed ranging between 55 and 70. After the first 40 miles, there were several stops. Then after the next 40 miles on return, and at the last stop the light came on upon restarting the car. I came home and ran the test using Autotap. Here are the results of the freeze frame data that it gets when the light was recorded in the system (per Autotap manual):

--------: FREEZE FRAME DATA :--------
Generated by DTC code: P0174
Fuel System Status Bank 1: CL-1
Calculated Engine Load: 40.4 %
Engine Coolant Temperature: 194 °F
Short Term Fuel Trim Bank 1: 10.2 %
Long Term Fuel Trim Bank 1: 19.5 %
Short Term Fuel Trim Bank 2: 10.2 %
Long Term Fuel Trim Bank 2: 19.5 %
Engine Speed: 2095 RPM
Intake Air Temperature: 73 °F
Mass Air Flow Rate: 4.373 lb/min

Here is the entire set of the same data:

Check Engine Light: OFF
Time Since Codes Cleared: ---
Distance Since Codes Cleared: ---
Drive Cycles Since Codes Cleared: ---
Confirmed Diagnostic Trouble Codes:
Code: Description:
P0171 Fuel Trim System Lean Bank 1
P0174 Fuel Trim System Lean Bank 2
Possible Diagnostic Trouble Codes:
Code: Description:
P1111 IAT Circuit Intermittent High Voltage
--------: EMISSION TEST STATUS :--------
Emission Status: <SELECT DATE>
Vehicle Model Year: <SELECT>
OBD Compliant: Yes
Misfire Monitoring: Complete
Heated Catalyst Monitoring: NotSupported
Comprehensive Component Monitoring: Complete
Catalyst Monitoring: Complete
Fuel System Monitoring: Complete
Evaporative System Monitoring: Complete
Secondary Air System Monitoring: NotSupported
EGR System Monitoring: NotSupported
Oxygen Sensor Monitoring: Complete
Oxygen Sensor Heater Monitoring: Complete
A/C System Refrigerant Monitoring: NotSupported
--------: FREEZE FRAME DATA :--------
Generated by DTC code: P0174
Fuel System Status Bank 1: CL-1
Calculated Engine Load: 40.4 %
Engine Coolant Temperature: 194 °F
Short Term Fuel Trim Bank 1: 10.2 %
Long Term Fuel Trim Bank 1: 19.5 %
Short Term Fuel Trim Bank 2: 10.2 %
Long Term Fuel Trim Bank 2: 19.5 %
Engine Speed: 2095 RPM
Intake Air Temperature: 73 °F
Mass Air Flow Rate: 4.373 lb/min

According to the manual, the system is asking for more fuel at 2095 RPM (I think), hence considered lean. I took the results to the mechaninc who scrached his head and said he cannot figure it out. I think I amy need to go to someon else since the problem registers more than once.

I also had the smog check done for California and the result were surprisingly wonderful. 0 CO2, 0 CO, and everything else was just wonderful. I am confused why this code comes on.

Any assistance, thoughts, help would be appreciated.

Thanks.

 

Abe:
The freeze fram data says you have a lean burn condition. Both banks. Why you get only one bank code is a mystery.
Either you most likely have low fuel pressure at speed (easily checked), vacuum leak (check the entire air inlet pklenum after the MAF, including breather hoses, brake booster hose, the plenum itself (I don't remember if the NA engines have plenum "resonators" but I found them cracked on two SC cars), or a bad MAF. The MAF values from thr freeze frame seem similiar to numbers my scanner produces, but do not seem to even be in the ballpark for an engine at speed. I suspect a multiplier or unit error in the scanner.