Hi everyone - I am new to this forum, so thank you in advance for your responses to my issue.

I have a 99 XK8 Conv with 96K miles, and about 6 months ago, my CE light came on with 02 lean codes and a "misfire" code (can't remember exactly now). Well, I cleaned the MAF and have been ok until a couple days ago. Now, I get 3 codes: PO172, P1111 and P1637 and the car is in "performance restricted" mode. I don't think I had the P1637 before, but am thinking maybe I just need to replace the MAF which might resolve all three. I don't have any real "symptoms" other than a little bit of a rough idle on occassion, which I know is indicative of a bad MAF. Thoughts?

Also, MAF's are pretty pricey - anyone know of a good OEM supplier for a reasonable price?

 

P1637 is a CAN bus fault. Here is the DTC guide for your car.

bob gauff

 

The MAFS would be a good guess to start. Rich is a little more focused than lean. The P1637 is saying that some sensor is not reporting within expected range. The P1111 is not an error code, it is saying that all system checks have been completed since last reset.

About $300 at the on-line suppliers, $150 used.

 

Thanks Bob - not sure what that means but I will read the doc. Is there any way you could email that to me? For some reason, it's saying my account does not have privleges to view the document??

My email is ssblast20(at)aol.com

Thanks!
Steve

 

The forum has some new member restrictions to reduce the affects of drive-by spammers.

Post a couple more times and you will have full privileges.

 

P1637 is a little more serious CAN Bus error. The CAN Bus is the major electrical artery between major computer modules - ECM, TCCM, ABS, BPM, etc. The possible causes could be several, but some common possibilities - defective cabling/harnessing on the CAN, module to module, shorts, opens between modules, or defective programs/modules. P1637 finds a fault between the ABS/TCCM and the ECM, so you want to physically inspect these circuits, but could also be a corrupted program, diagnostics corrupted, or bad module(s), etc.

My first approach and simplest would be to clear the code, see if it repeats, then if it does, begin diagnosing from there. Sometimes the startup diagnostics in one of these modules hiccups and will set the code.

 

Great info guys - thank you. I'll start with a new MAF first and see if that helps, and if I still have the P1637 code, then I'll start troubleshooting. Thanks again for the quick responses.

 

I have sent the DTC guide to your eMail

bob gauff

 

OK - I'm following up on this post from several months back. I am still getting po172 and po175 rich codes on my 99 XK8. Then the restricted performance kicks on and off as well. Slightly rough idle at times at standstill. I have recently replaced all spark plugs and seals, valve cover gaskets, replaced the MAF (new Cardone MAF, plus I had another spare - all 3 act the same so I think I ruled that out). We tested for vacuum leaks and don't see anything. Reset the codes and they come back on each time, same day. I could use some help. Thanks -

 

I had the same problem with my 2000 XK8, here's what I checked:

First, verify that both Long Term Fuel Trims (1 and 2) are showing negative values over 10. I expect this to be the case, but check just to be sure we're dealing with the correct problem from the get-go.

Then,

1. Verify that the MAF output varies smoothly with engine speed (not a single value or jumping between 2 or 3 static values) and see that the electrical connections are clean and tight.

2. Verfiy that the fuel pressure at the rail is to spec. for your model year. Also verify that it holds pressure after engine shut off.

3. Check the condition of the Fuel Pressure regulator and it's vacuum hose. Problems here will be revealed in 2, above.

4. Check that the AIT (Ambient Air Temp.) readings are correct (from the sensor, not the dash reading)

5. From a COLD start, check that the IAT (Intake Air Temp.) starts at about ambient air temps and warms to spec for your model.

Problems with 1, 2 or 3 can be addressed directly. Issues with 4 and 5 may cause the ECM to "see" the engine as cold all the time, thereby enriching the fuel delivery too much.

Beyond this, unmetered fuel could be entering through deterioration of check valves in the the fuel evaporative/purge system (I could use some help in better understanding and diagnosing this myself).

It could also be coming in through leaking/worn injectors. Though they would have to be leaking on both sides to trip both codes...it must happen because people rebuild them.

Rich codes are less common than lean ones and require more work to track them down. Experience is that they are almost always related to MAF problems. I know you replaced yours, but give that area a once over again...

BTW, the leaks you are looking for will cause a LEAN condition as unmetered air enters the system. While its good practice to button everything up tight, its not addressing your problem here.

Report back and good luck!

 

what about the air filter, is it clean and correct one? what does the throttle body look like, is it incredibly dirty on the butterfly and sidewall n(that you can see and reach)

I would think rich codes would be easier to track down...

 

I totally forgot about making sure the air filter is clean. A while back I did a test of MAFS readings with an old vs new air filter and the difference was enough to be a partial cause of my rich condition.

I guess I was thinking that rich codes are hard to dog down only in comparison to the much more common and easily caused lean codes. Regardless, they are all a pain

 

OK guys, it's been awhile since I posted an update on this one. I no longer have a CAN BUS error, and have not in months. Long story short, I have still been chasing both rich codes (PO172 & PO175) with RP kicking on/of as well. Here is what I've done to date:

*Spark plugs and valve cover gaskets changed (gaskets were leaking, plugs were a mess) - checked for vacuum leaks (none) etc. Codes still on.

*NEW Mass Air Sensor - vehicle drove better, rich codes came back= couple days later)

*New Air Filter - just to be sure.

As of yesterday, installed NEW Fuel Pressure Regulator and Hose.

Drove it last night, drove today, ran beautiful. I even gave it a fresh wax to say "thanks" for driving so nicely. Parked and cut off (for 5th time). Come out of store, start up, check engine light ON, Restricted Performance ON. Drove 2 miles, FP turned off. Have a single rich code: PO175 (bank 2). No sign of PO172 (yet).

This is driving me nuts....any feedback is appreciate of where to look next.

 

Sorry to "bump" this one up....just seeing it moving down the list and I'm getting frustrated with this rich code issue, and not sure what to do next. Please see the previous post, and thanks again for your comments!

 

Did you check the IAT and AIT sensors are working porperly? (From my post, above)

Any weird fuel smells from the evap system by the front drivers side?

Good move on the fuel pressure regulator. Did you check the fuel pressure leak down rate ?

Somewhere you have unmetered fuel entering...

 

my fuel pressure (since I've been running live scans alot lately trying to get some PID information) is right at 55.5 psi at idle, plus/minus a couple tenths.

 

Spurlee.....good questions. I gave my mechanic that list awhile back, but am not sure if he did those items before we realized the bad valve cover gasket leak. He may have just gone ahead with the other work and not checked those readings. I will have him check those next to see if that tells me anything.

On another note, I should point out that when replaced my mass air sensor, I did buy a replacement MAF sensor from partsgeek.com - it's just the sensor itself that bolts into the MAF housing, around $100. My mechanic said a few days ago to only buy MAF's from the dealer ($300). It was a CARDONE sensor - not sure if that was a bad move and can be part of my issue or not? Any thoughts? Thanks -

 

I bought a Toyota MAFS to replace mine ( GASP )...its a denso part just like the OEM, got it from NAPA.