2000 Boxster code 1502

porscheme · 07-23-2011, 06:48 AM

Got a P1502 fault code from Durametrics. Replaced throttle body. Seems to actually run worse than before, and still will not go over 2000 rpm's unless I clear the codes while it is running, then ok until the next re-start. Any suggestions?

JFP in PA · 11:07 AM

I'm not surprised changing your throttle body didn't do anything; P1502 is the code for either a bad fuel pump relay or a defective DME....................

mikefocke · 07-23-2011, 10:35 AM

Or a bad/dirty spring?

For the later year DME 7.2 986s "... the throttle is brought into emergency air position by means of two springs. This return of the throttle must take place within a certain time. If this time is exceeded, a fault is stored in the memory."

For the early 986s, JFP is quite right.

Posters asking for code insights need to specify the model year as codes do vary......

porscheme · 07-23-2011, 11:41 AM

disconnect the Mass airflow sensor, runs great.

Are the "springs" in the throttle body control module or the controller down by the pedal?

porscheme · 07-28-2011, 06:22 AM

So there are two answers? How can a code P1502 be weak or bad return springs, and the same code be for a faulty fuel pump relay? I guess I 'm confused. The Durametrics software points to throttle return springs but a thread here shows a fuel pump relay issue?

ABQautoxer · 07-28-2011, 06:59 AM

http://forums.pelicanparts.com/boxster-cayman-forum/515658-erratic-idle-p-code-p1502.html
http://www.renntech.org/forums/topic/30630-erratic-idle-code-p1502/

Since you say replacing the TB didn't work, could it be the connector?

porscheme · 07-28-2011, 02:42 PM

Yes I cleaned all the connectors with electronic parts cleaner. Checked the fuel pump relay, all looks normal. If I re-set the fault codes while the engine is idling, the engine runs normally, until you shut it off, and then it goes right back to no rpm's above 2000. Very confused, parked the car at night, all was normal, a few days later start the car and all this. Replaced the throttle body with a new bosch unit, replaced the MAF sensor, checked all the connections at the TB, MAF, the unit under the seat, and the wiring. All appear to be ok. Disconnected the battery, nothing. Disconnect the MAF and it starts and runs normal. The closest dealer I have is 3 hrs away in Quebec, Canada, so any help would be appreciated.

mikefocke · 07-28-2011, 05:08 PM

There is the hardware of the ECU and then there is firmware and a set of settings for a specific engine size and ECU firmware revision. The firmware has been revised several times (5.2, 7.2, 7.8 are revs numbers that come to mind) and the codes aren't always the same though when I looked this one up I was surprised at how different the meanings of the same P-code were. E-gas versus mechanical throttle activation meant a big revision and they repurposed the meanings of the possible codes I guess..

Which is why my above message suggests that a code always be accompanied by the model year (if everything is stock) or DME firmware revision number so the P-code can be looked up and the list of causes for that DME version can be cited. After all you could have a 97 model year with an engine from another year and a DME that goes with the engine and doesn't match the chassis.

JFP is a guru and he probably looked up the 1502 code in the 5.2 "book" but your Durametric results text implies you have a later 7.2 firmware revision.

When you disconnect the MAF, the engine runs without trying to adapt to what the sensors are telling it. When you reconnect, it takes a while but then adaptation takes place and if you are getting a bad sensor reading the CEL can get triggered because the ECU firmware knows that value just doesn't make sense.

"The position of the throttle is controlled by a digital position controller which emits a pulse-width-modulated (PWM) duty cycle and a direction bit." And the circuit diagram shows a 6 wire connector back to the ECU from what must be a position sensor probably connected to the throttle body. Unfortunately, the ECU manual only speaks of replacing the "throttle part".

Connector, wiring? Any work done near there before the CEL went off the first time?

porscheme · 06:09 AM

The cel light went on a couple of times last summer. That is when I bought the durametric software. Re-set and it would be ok for a while, then go on for no apparent reason. Figured the junk we get for gasoline might cause this. This was the first year I had given the car to someone for storage, and he had disconnected the battery for the winter. I wouldn't think that would do anything. I had driven the car around 4000 miles since I got it back. Could O2 sensors cause this? Also, would I damage anything by driving it after I reset the fault codes. Thanks for your input, I will be checking the wiring again later today.

Also, been hunting around online and found a few people on various sites experiencing the same exact issue, but never read about a resolution to solve the issue. Could it possibly be the Throttle position sensor under the dash or does the spring timing test apply only to the throttle body?

JFP in PA · 07-29-2011, 06:14 AM

Quote:

Originally Posted by porscheme

So there are two answers? How can a code P1502 be weak or bad return springs, and the same code be for a faulty fuel pump relay? I guess I 'm confused. The Durametrics software points to throttle return springs but a thread here shows a fuel pump relay issue?

As Mike has suggested, which DME version software is the car running? It should appear on the Durametric screen..................

porscheme · 07-29-2011, 06:28 AM

Motronic 7.2

porscheme · 07-29-2011, 06:34 AM

JFP in PA · 07-29-2011, 06:56 AM

That narrows the field; this code has multiple definitions, depending upon the DME version. With the 7.2 DME, you have a throttle body issue; the “springs” issue that Mike noted (this is housed in the side of the body itself). This can be caused by build up on the throttle plate itself, or the electronic sensor unit on the body. As yours is a new unit, I would think that build up is not an issue. Now the tricky part; if memory serves, there was an upgraded replacement throttle body released that required a “re-flash” of the DME to work correctly, this may be your issue.

When a new body is installed, you should run a short procedure to “set” the throttle motor; disconnect the battery for a moment, reconnect it. Turn the key to "on" but do not start or touch the gas pedal - wait 1 minute (you should hear a small motor on the throttle body engage and then reset) - turn the key to off and remove the key for a moment or two. Then reinsert the key and start the car, it should rev normally now. If it does not, you may need the re-flash. If that is the case, you may want to give your dealer a call with the new body’s part number and your VIN; they should be able to tell you if you are in the market for a re-flash.

porscheme · 07:31 AM

Thanks, I will attempt that right now....Update
Still the same. I guess I'll have to check on that re-flash.

porscheme · 05-11-2012, 01:52 AM

update. removed the ECU unit and shipped it off to ECUdoctors.com. They checked that, and then asked that I also ship the security box from under the front seat, as well as a key.

They reported that they could not find anything wrong with the system.

These were great people to work with. Highly suggest them!

The only thing I could see that happened was maybe when my girlfriend moved the front seat the morning the whole thing started, and maybe a connection to the box under the seat was loose? I hate intermittent problems, but a couple of thousand miles later and we are still ok.