Hi guys:

I’ve owned my 1999.5 XJ8 for over 20 years. Over that time, I’ve had Failsafe come up many times. I’ve narrowed it down to the TB several times, and have replaced the TB with a used part, twice.

My conclusion has been, the PPS (left side) fails and is not serviceable. The TPS (right side) is replaceable, but rarely fails. The only solution is to replace the entire TB. (I apologize for the acronyms, but I’m assuming anyone intimately familiar with the X308 TB problems will know what I’m talking about.)

Here’s the current code (1122) I’m getting, intermittently:
c

I bought a used TB (2000 XJ8, 88K miles) and got these codes (0122, 0222 & 1122):


Here’s where it gets weird. I assumed the replacement 2000 TB was bad due to age, so I reinstalled the old intermittently failing TB to verify. No code 0122 or 0222, but, after many hard resets, car was stuck in failsafe and kept throwing 1122, as shown in the first pic.

I gave up, and parked the car with no throttle (failsafe). Not wanting to just junk the car, I tried one more trick. I pressed the gas pedal before switching on the ignition, switched the ignition on and fully depressed the pedal. No Failsafe and no codes; car runs normally. (I saw somewhere, the relearning process is to turn on ignition, slowly depress the pedal and slowly release. I did that many times with these two TB’s to no avail. Only when I depressed Before ignition On, did this work.)

So, what is the proper relearn procedure?

Next question, should I return the 2000 TB as defective? The 0122 and 0222 codes make me think it is… (To make sure, I’m going to remount it and try the relearn process a few more time before I call the part “bad”, and return it. I tried that many times, but not pressing the pedal Before switching on the ignition and Before the computer triggered Failsafe. Pressing the pedal before Stability Control Failure is activated seems to be the key!)

And, one final question. It appears all TB’s, specifically the PPS portion, will fail. They’re all over 20 years old! You can’t buy a new one, but I’ve seen a TN company that refurbishes them. Is this the route to go?

I’d like to see as many of these fine old cars on the road as possible.

Any thoughts appreciated… Mark, in Texas.

 

Re the spare TB - Have it rebuilt instead of refund so you have a known repaired unit if and when it goes south.

Test both on the OBD reader, go to 'live data' scroll to pedal position, slowly depress the pedal and see if there is a smooth rise, if it hangs up or fails you've found the issue - worn tracks.

 

That's not a 100% sure way to prove the fault though. I agree with your logic but I've seen on other vehicles the issue only occurring when you've got the vibration of a running engine & sensor tests fine using your method. It's still worth trying though.

 

I had similar problems on my 1999 XJR. Would run fine then throw all kinds of throttle body codes. Turned out is was a problem with The TPS connector. The female parts had become loose and were not connecting well, Cleaned the male parts and replaced the connector and all is fine. Also the TPS is hall effect so no moving parts or tracks to wear out.

You can get the a pigtail or just the staight connector from:F4-013,4 Pin Connector,Toyota, Lexus, Ignition Coil,2JZ-GE Distributor Crank electronic connectors,,


https://www.connectorid.com/products...0-sealed-black

 

I've had a few PPS's go out over the years and just found the cheapest TB off eBay to get a PPS. The last time I did that, the PPS lasted about four months. So, I tried the place in TN, Automotive Scientific INC. That was a few months ago and so far their rebuilt PPS works like new. I also had them rebuild a bad one, so now I have a spare.

When I do any electrical work, I put a dab of dielectric grease on the female connector. That will help maintain good contact.

Their website is autoecu.com

 

Thanks guys:

All useful insights. I have a couple of spare TB's, so I think I'll use Autoecu for a rebuild.

On the connections to the TB, I've cleaned them and that seemed to cure the problem for a while, but the loss of communication with the throttle always returned. I have not replaced the connectors, but that may be a solution. As mentioned, after four persistent failures of the TB (over the last 10 years or so), the PPS seemed to always be the problem, and that stands to reason, given that the newest of these TB's are 23 years old! I think the PPS just wears out... Good to know there is someone out there that can repair them.

Many thanks for the contributions.... Mark

 

This thread reminds me that if I've ever got the spare cash I need to find somewhere in the UK to get my old TB rebuilt as a good spare. That had the same fault.

 

That's from my #1 post.

Does anyone have a relearn procedure that can clear the communication problem after a hard reset? I won't get around to reinstalling the (new to me) used TB until Friday. So, I want use the correct relearn before returning the suspected bad TB I just bought.

My old TB is working for now, but I'm pretty sure the PPS gremlin will resurface.

Also, take a look at the second pic in post #1. It shows p0122 and p0222. That's on the (new to me) TB. Does anyone know if that's indicative of a TPS failure, and that the PPS in this TB may be okay? I don't get those codes on my intermittently working TB.

I'm still planning to get one of my old TB's rebuilt by autoecu, but would like to get the car on the road with the parts at hand for now.

Many thanks... Mark

 

When you do a hard reset, all of what the ECU and TCU has "learned" is erased, so a "relearn" for both the TB and trans is needed for optimum performance. If you don't do the relearns, the modules will learn from your normal driving techniques. One important thing to do when fitting a PPS is to adjust the throttle cable to get the full range of travel. Your scanner should have a Live Data mode that gives information on all of the engine parameters. Look for anything that says "Throttle" and that should tell you the percentage of how far the cable is pulling the PPS through it's full range of travel. With the key on and engine off, slowly step on the pedal until it gets to the kickdown switch, or WOT to see where it's at. The cable is adjusted by turning the plastic nut where the cable attaches to the TB; turning it towards the engine will increase travel; turning it towards the firewall will decrease. 99% is the best to set the cable as you know you're at WOT. If you go to 100% you don't know if you've gone too far and the butterfly in the TB could be open too much. That's my "relearn procedure" as it does move the wipers in the PPS which is what you're doing.

P0122 and P0222 are TPS codes. I attached the code chart for the AJ27 engine as I'm assuming the '99.5 MY has that engine and you're replacing the TB with one off a '00.

 

Besides operating the throttle KEY ON ENGINE OFF to keep the engine from HIGH RPM on initial start-up there are ways to help the ECM 'adapt'.
We were issued a TSB back in the late 90s.

 

Many thanks guys:

Especially the charts and ECM adapt.

Now, I'm thinking the TB I just bought has a bad TPS (0122 and 0222 codes are new and not present on the current TB). I have a known-good TPS and can replace, but then that raises the issue of adjusting it. Also, not sure if my generic scanner has live data on the PPS or TPS. I have the Mongoose Jag cable and V125 software. Will that have the live data? I haven't tried it because the generic scanner is so quick and easy, and I know what the codes are telling me.

Also, do you think I can hook up just the electrical connections and throttle to the suspect TB for testing? Much easier than a complete R & R. My thought is, the System Check will trigger the TB codes (or make them go away) whether the engine is running or not...

Again, many thanks... Mark

 

Yea, I think the TPS is bad, too, with low voltage on both tracks. Here's a good thread on changing it out and doing the adjusting.

The Mongoose cable and software is dealer level stuff, so yea it has live data. I think you need a subscription (?)

And another "yea" If you can get the TB in a spot to plug in the connectors.

I forgot to address the trans relearn yesterday. My car has a different trans than yours, so I had to look for the procedure, which was easy with AI. I attached a word doc detailing what to do. As a disclaimer, AI says that it might make mistakes, so if there's any questionable stuff in there, Bob (motorcarman) can make corrections.

 

Thanks. That gives me lots of things to experiment with when I get back to trying to sort this mess.

The tranny relearn sounds a lot like the drive cycle to get the OBD emissions to set "Ready". Luckily, my current county doesn't require the test. In Houston, we would have to drive about 300 miles to get the minimum "readies" to pass the emissions test. Think of all the "emissions" that put out just to pass an emissions test! Lol.

Also, no subscription needed for V125, but needs Windows XP and Mongoose JLR cable (hard to find). I only have it because it's the only way to program the keys,

Regards... Mark

Correction: I have the V130 Jag software.

 

I was somewhat surprised when I saw the trans relearn procedure for the ZF. The SC cars use the MB 722.6 trans. The relearn is similar, but you only have to do it until you're satisfied with the results. I like mine to down shift into 1st gear before coming to a stop so that I'm ready to hit a hole if need be. We have a lot of stop signs around here where the cross traffic doesn't stop and the speed limits are 45 or 55, and a couple on the highway where it's 65. You probably have the same down there on SPI.

I don't have any inspections here. They only do smog in Las Vegas and Reno, so when my registration is due, they send an email, I send them money, they send a new sticker. And, I live 10 miles east of CA, so my friends over there get a little jealous when they see what I've done to hot rod my car and they're having to stick with the OEM intake and exhaust stuff. If I had to get a smog check, it would take a lot more than driving 300 miles to get the P1111 code.

You should be able to get that TB working soon. ASI will rebuild the bad TPS but I haven't seen this advertised on their website. In fact, when I went to their website while we've been chatting on this thread, I didn't see any rebuilt PPS's or TPS's advertised. I had ordered a PPS, which was advertised at (iirc) $250 with a $50 core refund. So, I called them and told them that I had three cores, but wanted one returned as a spare. The dude said, "sure, we'll credit you $100 and rebuild the spare for $100." So, give them a call and they'll work out a deal.

 

Here are a couple of things that might help those, like me, battling their TB:

1. You cannot test another TB without removing the old one, as I questioned in post #11. The electric connections won’t reach. More on that later.

2. I think, the correct Relearn for the TB throttle position is: after a hard reset, press the pedal immediately (before System Check has time to think) when turning the ignition on, slowly go to WOT and slowly release. Turn ignition off for a few seconds and back on, and see if Stability Control Fail (SCF), etc are gone. I was able to get SCF to disappear w/o a hard reset by pressing the throttle while switching ignition on, but it would come back once my foot was left the pedal.

Back to my situation, I had planned to test the TB that showing the faults in pic #2 in post # 1. That went to hell when my existing TB got stuck in Failsafe when I tried to pull the car in the garage. Long story short, I spend my time trying to get the car in the garage, only to find point 1 to be true: Testing requires removal of the old TB.

During the brief period the car wasn’t in Failsafe, I found my generic scanner does have Throttle % in live data. It’s about 2% at idle, car running, and about 60% at WOT, not running, of course. That doesn’t tell me much, other than the PPS and/or TPS seem to be working, until they are not. In Failsafe, the % goes to about 7% regardless of pedal position. No surprise there. That’s why it’s called “Failsafe”, and not “WOT”.

So, I’m kind of back to square one, with a suspected bad TB I just bought, but may be fixable with a TPS replacement. Current TB has a bad PPS, Or so I think….

Thanks again for the input. It helps… Mark

 

They are expensive, but if you can afford it SNG do have a version of TB new
https://www.sngbarratt.com/English/U...ttle%20body%60

 

Thanks. That is rather pricey. I checked and they don't seem to have the 99.5 - 03 YM TB. C2A1445 is "Unavailable - No Longer Manufactured".

Regards... Mark

 

I asked aj27 tb from barrat couple of years ago when they still listed for backorder. It was unavailable even then.