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Old 05-05-2016, 08:35 AM   #1
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No throttle response

My 2000 Boxster has rough idea, and no throttle response. Any ideas ????
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Old 05-05-2016, 10:47 AM   #2
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Upland, can you pass along some more info?

Has it run well in the past?
Can you give us a little history on the car (mileage, previous owner, other problems)?
Do you have a CEL?
When you say no throttle response, will it not rev at all?
Does it idle rough, or does it attempt to idle then die?

Sorry to bomb you with questions, but rough idle/no rev...there are a million things that could be wrong, and more info can help us narrow things down a bit.

Kevin
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Old 05-06-2016, 03:45 AM   #3
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It ran fairly well since I purchased it in may of 2015, but it did have a noticeable lag in the throttle
No info on previous owner. When I press throttle pedal tach only rises maybe 75 to 150 rpm and engine shuts off when I release pedal. Did a DTC read and got a code P1502
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Old 05-06-2016, 04:31 AM   #4
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Originally Posted by Upland54 View Post
It ran fairly well since I purchased it in may of 2015, but it did have a noticeable lag in the throttle
No info on previous owner. When I press throttle pedal tach only rises maybe 75 to 150 rpm and engine shuts off when I release pedal. Did a DTC read and got a code P1502
Aha.
Try this. The P1502 code may show on your code reader as a Fuel Pump Relay issue but I believe that it's actually a throttle body error code (Throttle Jacking Unit Spring Test).
You might try cleaning the throttle body (Stevedox recently did an excellent DIY thread on this) and then remap your EGAS system (turn the key to on for a minute and then off for ten seconds and start the car).

Edit: forgot to mention that there is also a throttle body position sensor on the side of the throttle body. It's a little spring thingie. It may be broken or gummed up. It's a fairly cheap part (for a Porsche). You might just replace that while you're cleaning the throttle body.

What the code is telling you is that the throttle is not returning to position fast enough when you let off the gas.

Last edited by Need_for_speed; 05-06-2016 at 04:59 AM.
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Old 05-06-2016, 05:00 AM   #5
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Originally Posted by Need_for_speed View Post
Aha.
Try this. The P1502 code may show on your code reader as a Fuel Pump Relay issue but I believe that it's actually a throttle body error code (Throttle Jacking Unit Spring Test).
You might try cleaning the throttle body (Stevedox recently did an excellent DIY thread on this) and then remap your EGAS system (turn the key to on for a minute and then off for ten seconds and start the car).
P1502 is the correct code for a faulty fuel pump relay, often a short to the B+ pin. You can check the relay circuits for signs of a short, or just replace it as they are not expensive.
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Old 05-06-2016, 05:26 AM   #6
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If it is a Fuel Pump relay, be thankful you got symptoms and a code. When mine went, the only symptoms were engine died and after 10-15 mins, it would start again. Never had a hint it was going until I stopped at a red light, engine died, engine wouldn't turn over until the relay cooled down.
When you engine is running, if you touch the Relay, it will probably be very hot.
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Old 05-09-2016, 08:11 PM   #7
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Well guys, I changed the fuel pump relay, nothing changed. Any suggestions ?????
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Old 05-10-2016, 10:12 AM   #8
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For the whole story, search on "Mystery problem, limited revs".
Here was the solution:

"PROBLEM SOLVED - In the end, it was the P1502 code that was the problem and the cure. My new Can-Tech OBD II tool showed the P1502 code and below it it said "Fuel Pump Relay End Limit. Porsche Part $11" Seeing this I assumed it was a Fuel Pump Relay code. After changing the fuel pump/sending unit/fuel filter and trying out my new fuel pump relay, I was discouraged so I texted my buddy who is the head mechanic at the Porsche dealership (yeah, tried to do it without him) and he said 1502 was a throttle body error code. Not happy hearing this, I opened my Bentley Service Manual and looked it up.

P1502 - Throttle Jacking Unit Spring Test

I almost crapped my pants. Why the hell did the OBD reader say "Fuel Pump Relay?" I couldn't believe it. I took the TB apart, cleaned it real good, exercised it, put it all back together, and started it up. Very rough idle but I could get it to 2300rpms!! On the right track I said! So I did the EGAS remapping thing where you turn the key to on for a minute and then off for ten seconds and start it. same thing. Then I cleared the code with the OBD reader and started it up.

OMG, it was like a new car. Not only did I have my revs back but after the car got to temperature, there was no flutter in the idle. I was so happy, I took it out and set a personal record for fastest speed on four wheels. 145mph

The throttle body wasn't really THAT dirty so I think I am just going to order a new one and throw it in there so I don't have any issues in the future.

I want to thank everyone who contributed to the effort in getting my baby back to normal. Got 3 days at Watkins Glen August 22nd, 23rd, and 24th. I was starting to sweat a little."
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Old 05-10-2016, 02:18 PM   #9
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Quote:
Originally Posted by Need_for_speed View Post

I almost crapped my pants. Why the hell did the OBD reader say "Fuel Pump Relay?"
Maybe because it is a generic code reader, not one Porsche specific
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Old 05-10-2016, 04:10 PM   #10
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[QUOTE=Need_for_speed;495454]For the whole story, search on "Mystery problem, limited revs".
Here was the solution:

"PROBLEM SOLVED - In the end, it was the P1502 code that was the problem and the cure. My new Can-Tech OBD II tool showed the P1502 code and below it it said "Fuel Pump Relay End Limit. Porsche Part $11" Seeing this I assumed it was a Fuel Pump Relay code. After changing the fuel pump/sending unit/fuel filter and trying out my new fuel pump relay, I was discouraged so I texted my buddy who is the head mechanic at the Porsche dealership (yeah, tried to do it without him) and he said 1502 was a throttle body error code. Not happy hearing this, I opened my Bentley Service Manual and looked it up.

P1502 - Throttle Jacking Unit Spring Test

I almost crapped my pants. Why the hell did the OBD reader say "Fuel Pump Relay?" I couldn't believe it. I took the TB apart, cleaned it real good, exercised it, put it all back together, and started it up. Very rough idle but I could get it to 2300rpms!! On the right track I said! So I did the EGAS remapping thing where you turn the key to on for a minute and then off for ten seconds and start it. same thing. Then I cleared the code with the OBD reader and started it up.

OMG, it was like a new car. Not only did I have my revs back but after the car got to temperature, there was no flutter in the idle. I was so happy, I took it out and set a personal record for fastest speed on four wheels. 145mph

The throttle body wasn't really THAT dirty so I think I am just going to order a new one and throw it in there so I don't have any issues in the future.


Once you price a new T/B you may change your mind. If you want a good used one I'll ship you one for $50 pm me
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Old 10-21-2018, 09:00 AM   #11
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Would you please share how you cleaned the throttle position sensor?
Thank you
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Old 10-21-2018, 09:02 AM   #12
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Please excuse my previous message. I did not have my glasses on, I misread it.
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Old 07-04-2019, 10:57 AM   #13
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Angry 986 Boxster In Limp Mode
My 2000 Boxster roadster with 2.7 is in limp mode. I have a P1502 code

My generic scanner say is it is "fuel pump relay end stage. I have read where it is actually "jacking spring" issue
If I clear the code, the engine smooths out and runs correctly
I have removed the throttle body, cleaned it and reinstalled. Problem remains.
The problem remains even after installing another throttle body,
I cleared the codes, recalibrated the throttle body by turning on ignition for 60 seconds(without touching the gas pedal), turning ignition off for at least 10 seconds, then turning the ignition back on, P1502 code reappears

I would really appreciate any advice on how I can get back on the road!

-Is the throttle body the problem?
If not, where should I look?
If the TB is bad, is it OK to try a used one or an aftermarket TB

Thank you

Bob
Nashville, TN area
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