My service engine soon (SES) light came on indicating a mass air flow sensor code. I replaced the mass air flow sensor, cleared the SES code, but it came back on about 30 minutes later reading the same mass air flow sensor code. Any ideas of what could be happening since I've already placed the mass air flow sensor and my SES light is coming back on?

 

marques, check the wiring going to the MAF. It is possible that it has gotten damaged and that is causing your issue. Beyond that, hand over hand the wiring to see if you have damaged the wiring anywhere else.

 

I actually had this exact same issue in my X-type. I ended up replacing 2 MAF sensors, only to find that there was a vacuum leak in the Brake Booster line. Check all of your vacuum hoses, and apply silicon to the base of the hose connectors if possible. It took us weeks to figure it out, kind of a pain in the ***.

 

Hi there guys,i just change the MAF and still having error codes P0171 and P0174
Are these codes for the MAF or is an other error code for the MAF?

 

Chrys, those codes you have are simply saying that you have a vacuum leak on both the front and rear banks of the engine. This can be caused by a few things. Normally, you are looking at a leak somewhere between where the MAF Sensor is and where the intake splits into the front and rear banks. So, you can have a rip in the rippled tube just in front of the throttle body, you could have a bad seal on the outlet of the throttlebody, or the MAF sensor being dirty/bad. From there, you start getting into multiple faults and most likely, you are looking at bad IMT valve o-rings in this case. You would also want to check the tube going to the PCV valve and also the hose running from the intake to the brake booster. All of these are capable of causing what you are seeing.

 

And while checking for the leaks you might want to use the old practice of spaying starter fluid towards any place where you suspect a leak. If the leak is there the fluid will get sucked in and the engine will momentarily speed up, no change in idle speed no significant leak at that point, move on...

If nothing turns up then the problem is more complex (and we'll let Thermo's wisdom guide us there!) but this is, at least, a pretty quick and easy way to search for "obvious" leaks.
================================================
Jaguar: Grace, Pace, and Space - Sir William Lyons

 

Totally called the Vacuum leak. Those were the same codes mine was throwing.

 

I'm having a similar problem. The idle runs up and down btwn 1500 & 2000 rpms searching for the correct idle. When I did my spark plug change a while back I forgot to replace the large clamp ring that seals the rippled tube and I had this exact same behavior; idling all over the place. Thing is, when I did put it on, problem went away immediately.

Thus far I have ensured there is no leak at the rippled tube, and the PVC tube. I also removed and cleaned my MAF sensor which was very dirty, but no dice!

I will do the carb cleaner spray search on the brake booster lines tonight. But I kind of suspect the harness to the MAF. Mine has no play as it breaks out from the larger harness, very tight reach to the MAF plug. When I took apart the air box this time to replace the upper radiator hose assy. I had to lay the air box lid across the top of the motor to get it out of the way, and this probably further stretched those wires. In any case, how would one perform a continuity test on the harness???

 

Patterson, the easiest way is to use a paper clip and run it between two pins at the plug going to the ECU and then going to the other end (ie, MAF sensor) and then doing a continuity check that way. That makes it a single person job. If you have two people, then you can make yourself a long set of leads and then you can probe each end of the wire at the same time to see if you have continuity that way. The big thing is having drawings that show you wire color and pin location. You will find that there are a few wires that are going to have the same colors and just because they look the same, they may do completely different things and will not be electrically tied to each other.

For reference, any wire in your car should have a resistance of less than 0.5 ohms if you are not running through any component (ie, MAF sensor, blower motor, etc). if you are seeing more than that, then that is a sign that you are starting to see issues. But, odds are, you will see either cracked insulation or melted insulation if you do a visual inspection of the wire if you are having issues. The other check is to roll the wire as if you were trying to roll it around a pencil (slightly larger diameter rod if looking at 10 gauge wiring or larger). If the wiring makes a sharp bend, then you have a broken wire inside the insulation.

 

I'm sure between Thermo and Pab you're already "sorted". But....just to add my half cent; My Jag guy said that many Jags he gets in with MAF problems are using K & N air filters. He said something about the oil from the wax being a nasty bit of business for the sensors --correction he said it was from people "over oiling" them 0.o.

 

Thanks Thermo, I guess we just need a schematic or at least a pin-out of the plugs that go into the ECM? Then we could establish continuity from the sensor plugs back to the ECM. That would be awesome b/c it would remove a lot of questions. I like the rest of what you said and I think I have a method for checking the continuity of the plug that goes into the MAF. I will ignore the main harness but check continuity of the wires coming into the plug, and 1" or 2" aft.

SB, I thought about that too; I cleaned and oiled my K&N air filter before putting it all back together, and I was pretty generous with the oil spray. Maybe I should run a clean Fram and see if that does anything? lol! For now the Jag is parked with the battery disconnected in hopes the computer will reset itself after 24hrs.

Now I'm buying Snake Oil, but it's cheap!

 

I did the carb cleaner spray test but no change in idle speed for any of the hoses going into the manifold or the MAF seal, or MAP seal.
It's probably not a vacuum leak.
I figure it's an electronic malfunction somewhere.

 

Yes, the key with K&N filters is not over oiling them. It is easy to tell if you have over oiled them. You simply remove the filter and see if you can see a streak running up the intake from where the oil has run. if you have over oiled, remove the filter, wash and spray again (using less oil), wipe out the intake and then clean your MAF sensor (if you don't clean the MAF, you are still going to have issues).

I have been running K&N filters in my vehicles for the last 10 years. No issues. If anything, it has probably saved me from destroying an engine. But then, when you go through 4 feet of water in a truck and the water is coming up over the hood, the ability of the oil in the filter to repel water was important. It isn't the product that is bad, it is how people use it.

 

Thermo is on point with product missuse. People have a tendency to think "if I use more it's better" look around at the missuse,hair spray,hair jel,lipstick, mascara, tattoos,nose rings, medication (if one works hell take four). Just a Friday rant, Have a good week-end guys.

 

I probably went a little over board with the oil on the air filter. I'm going to pull it, clean it, and, clean the intake tube and air box. Check for rips or cracks in the rippled hose to the intake, and, clean the throttle body.

I got the codes read tonight:
P0507, P0456, and, P1111

The first one is IAC (idleaircontrolvalve)counts are higher or lower than expected, the engine speed is not in its expected range. <this has become painfully obvious!

Possible causes: Vacuum leak
Dirty throttle body
IAC motor defective
Poor electrical connection to the IAC valve

P0456: Large leak in the Evap system
Possible causes: Defective, loose or missing fuel cap
Evap canister broken, hose cracked or not connected
Purge or vent solenoid defective
Vacuum leak

P1111: IAT (intakeairtemp) intermittent high voltage-low temperature condition
Possible cause: Open circuit to IAT
Failed IAT

Any thoughts? Recall that the crazy idle speed started after I removed the air box to replace the upper radiator hose. I replaced the air box very carefully but with a heavily oiled K&N air filter. The point is I didn't touch the IAC, or Evap system, or the IAT. I think I know where the IAC is, on the manifold near the windshield. No idea of where the Evap canister is. Ditto on the IAT. So how would any of you proceed?

Thanks!

 

Patterson ,the IAC is built into the throttle body. If you look on the throttle body, you will see a small hole on each side of the butterfly valve (large metal plate that blocks the air flow). Take some throttle body cleaner (not carb cleaner) and spray it down that hole. Might as well clean the whole throttle body at this point too. That should clear that up.

As for the P0456, first check the gas cap. That is what normally creates issues. After that, it is going to be a hand over hand of the system to determine where the leak is. But, 99% of the time it is the gas cap.

 

Today I put in a new, regular air filter, a new gas cap, and cleaned the TB. I also cleaned the K&N oil from the air box and inspected the corrugated tube for cracks; it had none.

I did find a small leak on one of the brake booster lines that goes into the top of the intake manifold. But I had no way of sealing it. I made a feeble attempt at wrapping the insert with a layer of electrical tape but the tape backed off when I pushed the line into the manifold. I found the leak by spraying TB cleaner. The idle changed just a little, but it was repeatable.

Considering the codes I'm getting, I'm not messing with the MAF and I don't want to start buying sensors somewhat blindly and installing them, so I'm going to take it to the dealer this week.

I'll keep ya posted!

 

Check out this thread... had the same leak as you.
HTHs
Gary

https://www.jaguarforums.com/forum/x...anifold-71249/

 

I had the same check engine light problem, replaced the MAF sensor and got rid of the K&N filter. Works great now.

 

I replaced both of the inserts on the top of the intake that connect the brake booster vac lines, and put in a new PVC (crankcase breather), and no change!

I took it to the dealer today and they want to replace the throttle body for $2,200. I located a used one that has 86K on it for $460.00. However, I don't think my entire TB is bad. I think it might be the TPS. The throttle goes wide open, it's just coming back down that it makes the car jerk. It accelerates good, but can't idle correctly, always searching btwn 1500 and 2000. It doesn't stall, and, cruise control works! But, if I press the decelerate button, it's jerky.

Has anyone removed the TPS? I hear it's a weird sized Torx bit, like btwn T15 & T20? Btw, the Jag dealer does not sell the TPS alone, you have to buy a throttle body for $1,800.

On a side note, I left the car there and got a ride home while they looked at it. The dealer sent a Lexus tech. to come get me from my house so I could get my car back. After talking to him on the ride; I don't think he even knows what a throttle body is. lol! ...bag of rocks!