My car went into failsafe mode and threw the code P1573 throttle position not available. Does anyone know where I can find the TPS sensors without replacing the whole throttle body?

 

I rolled the dice on a used guaranteed TP on eBay for my buddy Todds 2005 S Type a half a year or so ago. I believe it was about $40. 00 shipped. It works fine to this day.

 

Be sure it's not a false code due to a failing battery.

 

I've dealt with that already on this car and I could unplug it and jumpstart it and the code would go away. I've tried cleaning the plugs, resetting the car, everything and it goes into failsafe as soon as I turn the key. I've checked all sensors relating to throttle and pedal position and they are clear of any corrosion and firmly connected. I just want to get the sensor replaced and pray it's not a wiring issue.

 

Did I understand that correctly? The poor car won't start unless you give the battery a jump? Yikes!!! If that is the case, take care of that before anything else. Most likely you'd be looking at a new battery.

 

Do you have access to a scanner that can read TPS and APP request's? These reading's need to be in very tight tolerance's of the vehicle will go into fail safe mode in a New York minute.

 

I've already replaced the battery. I'm saying it started throwing false codes due to a failing battery a few months ago. I replaced the battery which fixed the issue. This is an entirely separate problem. It sat for a week or so before I got around to replacing the sensor and so I took the battery out and charged it while I took the old Tps off and put the new one on, and once the battery was fully charged I put it back in and it ran fine... for about 3 days. It shouldn't be the battery again this soon but its throwing the same code for the TPS right after I replaced it.

 

A few thoughts come to mind.

Have you checked the charging system? Could be your perfectly fine new battery is not getting properly charged and is slowly running down while driving. This is quick and easy to rule out. On an early model, you should see about 13.5v at the battery while at idle. If the engine won't presently run with this code, just charge the battery and see if that makes any difference.

Take a look at this thread, for a similar fault on a later model. Not all details apply to a 2000, but this should give you some ideas:

https://www.jaguarforums.com/forum/s...solved-227450/

The basic gist was low reference voltage to the many engine sensors caused a spurious TPS code. Early models have a 3 channel TPS, while later models only had 2 channels. But I think the basic premise is the same, namely low reference voltage will cause a TPS code before anything else is flagged.

In that example, the root cause was a bad relay feeding the engine computer. Low input voltage to the computer caused low reference voltage output. The relay nomenclature and location on your car will be different. The suspect relay is R14 under the hood. Swap that with another relay of the same size from another system that is known to be working properly and see if that helps.

If swapping the relay is no help, check the reference voltage to the TPS. You should see right around 5.0v. If much lower, you'll need to investigate why.

 

may sound like something I should know, but would you walk me through the process of checking the voltage? I'm good with parts and wrenching but trying to understand wiring diagrams just makes my head hurt.

 

I'd be glad to help. No guarantee you've got low reference voltage to the TPS, but it's quick to rule out. Wiring diagram below, scroll down to fig 03.4. This wiring diagram is laid out kinda funky, with the text in the first half, and the actual diagrams in the second half:

http://www.jagrepair.com/images/Auto...01999.25en.pdf


Note the TPS along the bottom edge of the diagram, towards the right. Unfortunately, the innards of the TPS are not detailed. I'm pretty sure the two wires at the left (PI16-4 and -7) are the reference voltage circuit. That would be the yellow (Y) and brown (N) wires. But to confuse us, there are TWO yellow wires and TWO brown wires at the TPS connector. What dirty pool! Now that I think about it, I believe there are actually two separate reference voltage circuits for the TPS. This second circuit is probably the two wires at the right, (PI16-3 and -6) If you can find any numerical identifiers on the connector, that's good. If not, we can still muddle through.

Turn on the ignition, but don't start the engine. If you can backprobe this connector (use thin rigid pieces of wire) while installed, that's best. If the back of the connector is sealed, you'll have to disconnect it and probe the face. Measure the voltage at the first set of yellow and brown wires, which should be pins -4 and -7. With one meter lead on -4 and the other lead on -7, you should see right around 5.0 volts. Then measure the second set, which should be -3 and -6. Again, you should see 5.0 volts, or very close to it. This is a regulated voltage coming from the PCM, so it should be very close to 5.0V. If you had to remove the plug for this check, reconnect it for the next step.

The next thing we should check is the voltage feeding the PCM. At the left of the PCM in that same diagram, follow the 66P and 67P (in a circle) at the left. These lead you to the top two symbols on fig 01.6. These two wires get battery power, switched on/off by Powertrain Control Relay #1, located at position R14 under the hood. Note there is no fuse between that relay and the PCM. Fuses are a handy place to measure voltage, but we can still check the voltage at either fuse #5 or #6 in the same panel. If the engine will start, go ahead and fire it up. If not, just turn the key to Run. Take a quick measurement of voltage across the posts at the battery. Engine off, you should see around 12.5 or so. Engine running, you should see right around 13.5. Now move up front, and put your meter's black lead on a good ground. Touch your meter's red lead to either fuse #5 or #6. Don't remove the fuse, just touch the exposed metal in the little recessed opening on the head of the fuse. Either side of either fuse is fine. The voltage you record now should be within 0.5V of what you recorded back at the battery. If the difference is more than 0.5V, try swapping Powertrain Control Relay #1 (position R14) with another relay of the same size. See if that narrows the difference.

Try those quick tests and report back with the numbers. Hope they don't sound too confusing.

 

Any updates?

 

Haven't had the chance. Will tinker with it tomorrow and report back with what I find.

 

update: officially ****ing confused. Bought another new battery, charged it and threw it in, no change. Bought a BAFX reader and used that to clear codes to make sure I was still getting the code and that it wasnt just lingering, and it kept throwing the code. I scoured the harnesses for any sort of short or exposed wire that would cause an issue and found nothing. Plugged it all back in and lo and behold, no more codes. Car is still doing fine a week later. Not sure what I did or why it decided to take 3 weeks to accept the new TB. I probably sound like I'm full of ****, cause I would think that too. Absolutely no idea what fixed it, but I'm just happy it's running and I can drive it again.

 

The problem could have been as simple as a dirty connection somewhere. Reseating that particular plug may have been enough to scrape it clean and re-establish a good connection.

If the fault returns, I'd suggest reinspecting all of the connectors you had disassembled. Hit them with some DeOxit D5 spray. This is NOT ordinary contact cleaner, so don't cheap out. I love the stuff. If the root cause had been an intermittent connection, this stuff usually takes care of it.

https://caig.com/deoxit-d-series/

Did you ever run the electrical checks listed in post #10? And did you swap relay R14?

 

yes, everything came back fine. I did swap that relay with a new one upon your suggestion. Havent had any issues since.

 

Cheers!

Thanks for the update.