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help car in limp mode P1688

Old 12-21-2008, 01:57 AM
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help car in limp mode P1688

Hi there

Help needs

No Mazda dealers in Pakistan. Rolls yes/ Range Rover / BMW yes yes just not mazda ford and alfa romeo.

My 2004 auto is giving me trouble. 61k km oil change every 1500 km. Changed coils and plugs 4 k km ago. The car about two weeks ago just blew the Bose Amp. I tried to get it fixed but will probably have to get a new one. A couple of days later on starting the car it showed the CEL and went into limp mode. Got my diagnostics out and it shows P1688. Which is the oil metering pump circuit.

Then got the engine cover off and the battery and everything. A water/coolant pipe juts above the oil pump/metering pump had leaked and coolant got into the connector. Fixed it. The car had not overheated and the coolant loss was only a drip and minimal but certainly into the connector. Got the sensor out and the wire and had it cleaned and the connectors dried out. Removed the CEL but it came back again and car started in limp mode. Cleared KAM in desperation and same thing happened but for the fact that it started stalling at idle as well.

Restarted it a few score times and it once went out of limp mode.Drove it in limp mode 25 km to my home. Got fed up and parked it in the garage alongside with classics and used the FD for four days. Restarted the RX8 and it ran fine... no issues.. good performance. Switched it off ... same thing ... ran fine. Thought problem had gone away. Used it all evening...several starts. went to a friends... parked outside.. temp 12 celsius. Came back... limp mode again. CEL P1688

Is it the oil metering pump? Is it the sensor? Do I need to replace the wiring as well. I need the part numbers for the harness, Pump and sensor as well. Also the Bose amp.... thats where it all started. Could this be linked.Shall I just get a good electrician.


Help guys.
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Old 12-21-2008, 02:26 AM
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Sounds loike you may still have an issue with the connector . I think there is a product you can spray on the connectors to help with this .
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Old 12-21-2008, 04:36 AM
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There is a positioning switch in the "sensor" If it is crapped up inside it won;t work properly. I would try and clean it inside with contact cleaner..and then reset it.

You will likely have to remove the pump...and manually return it to the zero position by hand..and then reset the switch so that it reads zero...and then it should work

Did you remove the sensor to clean it out?..if you did and didn't reset the pump that is what started the problem...

PM me if you have any questions
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Old 12-21-2008, 09:37 AM
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Zeroing the MOP pump

Originally Posted by dannobre View Post
There is a positioning switch in the "sensor" If it is crapped up inside it won;t work properly. I would try and clean it inside with contact cleaner..and then reset it.

You will likely have to remove the pump...and manually return it to the zero position by hand..and then reset the switch so that it reads zero...and then it should work

Did you remove the sensor to clean it out?..if you did and didn't reset the pump that is what started the problem...

PM me if you have any questions
Thanks a lot. will try it... By the way... I am a doctor so kindly forgive the idiotic question... how does one reset the pump to zero .. any links would be appreciated.
Cheers... will keep you posted
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Old 12-21-2008, 09:46 AM
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Are you doing the work yourself? If you are then the easiest way is to remove the pump from the car...and the switch ( black thing ) and turn the rotating piece clockwise to close it all the way..then carefully put the switch back on in the rotated position as well....then re-install the pump

What's wrong with being a doctor
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Old 12-21-2008, 10:29 AM
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Originally Posted by dannobre View Post

What's wrong with being a doctor
Unless of course he is a Proctologist!
Reminds me of Kramer having the "*** man" license plate!
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Old 12-21-2008, 11:38 AM
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help MOP p1688 and profession

Originally Posted by Mazurfer View Post
Unless of course he is a Proctologist!
Reminds me of Kramer having the "*** man" license plate!
He He... neurosurgeon actually... put that in as I am not an engineer and so would need guidance. I suppose mechanically electrically proficient guys would need less.
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Old 12-21-2008, 12:00 PM
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/\ kind of like giving us "learn as you go" instructions on brain surgery ? lol
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Old 12-21-2008, 12:32 PM
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dude, you're not getting any where near my brain !!!
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Old 12-21-2008, 12:43 PM
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/\ there is a first time for everything - even brain surgery . I dare say you would practice on less important people and work your way up ....
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Old 12-21-2008, 12:52 PM
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I could think of a few But he's almost gone anyway
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Old 01-08-2009, 09:25 AM
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thanks guys... got it fixed... took down the pump as advised ...rezeroed it and the sensor and its been behaving for the last four days now....
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Old 02-03-2010, 09:44 PM
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Hey Kamhus,
Can you please let us know about your OMP/DTC1688 problem. What is the outcome? If this (or OMP related) problem appear again?
I also have similar problem (DTC1686) and now in the process of deciding the best approach to it...
If anyone can give me any advice - you're more then welcome!
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Old 03-21-2012, 02:51 PM
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This thread helped me a lot
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Old 05-10-2015, 02:02 AM
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Hi,

I just swapped "new used engine"(4port euro 5speed manual).

Swap went great, started right away(new coils,plugs and plugwires etc.). new engine was just a block. So
i took omp from old engine. And now after couple seconds of starting i get CEL and P1688 code

I've tried to adjust OMP position sensor "couple" of times(just unbolt the sensor and turn). One time we got about 15mins of running before CEL.

Checked all the wiring followed by Service Manual P1688 DTC. No problems.

I put some premix on fuel to just to be safe before limp issue is fixed.

Couple questions:

- Could omp be on wrong position?(need to remove OMP from engine and turn/reset from back?)

- Switch/sensor is broken (measured about 60-80ohm on ends and there is a gap on the about middle of turning) what is the correct ohm value?
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Old 05-15-2015, 09:55 AM
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Can anyone help?

I had this code as well and tried to reset it with no luck so I bought a used one off ebay and installed it. The car ran great for about 30 miles with many stops and starts, now the code is back and I'm in limp mode again! I don't know why this is happening although I did replace an oil cooler line with a custom line to save money and i don't know if it's changed the pressure and burning out the pumps? Any thoughts I'm in desperate need of help at this point.
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Old 05-15-2015, 10:03 AM
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It has nothing to do with your oil lines.

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Old 05-15-2015, 10:48 AM
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I will take a look at the wiring and clean up the connectors and go from there I guess, do these pumps have to be adjusted when installed
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Old 05-15-2015, 10:54 AM
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TX

Originally Posted by ltchad5 View Post
I will take a look at the wiring and clean up the connectors and go from there I guess, do these pumps have to be adjusted when installed
The position switch on the pump may need to be adjusted.
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Old 05-15-2015, 01:56 PM
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Now when you adjust that sensor does that mean that the pump is in its last leg and will need to be replaced sometime in the future or can it be a more permanent fix?
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Old 07-10-2019, 06:58 AM
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P1688 - permanent deleting from ECU?

Hello guys!

I got P1688 (OMP problem) in 2004 RX-8.

can it be deleted and permanently erased whole thing with some software? To manipulate ECU so it doesnt matter.

I have checked OMP etc and I oil my car with 2-stroke to gastank.

So I just want to get the code away.

And... my car is also in limp mode, ofcourse.

Please help - software and advices needed.
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Old 07-10-2019, 10:47 AM
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What means rezeroing?

Originally Posted by kamhus View Post
thanks guys... got it fixed... took down the pump as advised ...rezeroed it and the sensor and its been behaving for the last four days now....
What did you meant by saying rezeroed?
I have same problem. Got to take pump out and fix a little bit. 🤦*♂️
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Old 07-10-2019, 10:09 PM
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Originally Posted by juspe View Post
Hello guys!

I got P1688 (OMP problem) in 2004 RX-8.

can it be deleted and permanently erased whole thing with some software? To manipulate ECU so it doesnt matter.

I have checked OMP etc and I oil my car with 2-stroke to gastank.

So I just want to get the code away.

And... my car is also in limp mode, ofcourse.

Please help - software and advices needed.
I had this problem on and off for about a year, I tried to zero it and it didnít work out for me. What Iíd suggest that worked for me is to go on eBay and get one used for $200. Replace it yourself as itís only 3 bolts and one wire. I think itís worth the risk buying a used one as they are $1500 new. One tip on drivability is that you may be able to disconnect the battery once or twice with it unplugged for 5-10 minutes and then turn it back on and that may get you by for a few days. Best of luck
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Old 07-11-2019, 12:42 AM
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Originally Posted by ltchad5 View Post
I had this problem on and off for about a year, I tried to zero it and it didnít work out for me. What Iíd suggest that worked for me is to go on eBay and get one used for $200. Replace it yourself as itís only 3 bolts and one wire. I think itís worth the risk buying a used one as they are $1500 new. One tip on drivability is that you may be able to disconnect the battery once or twice with it unplugged for 5-10 minutes and then turn it back on and that may get you by for a few days. Best of luck
Thank you for the answer.

So there is only 3 bolts and few electricity wires, I saw pictrures on that and have done research a bit.

So you mean that there is one Ēoil wireĒ/Ēoil hoseĒ also?
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Old 07-11-2019, 06:51 AM
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I did it a few years ago so I just looked at the part again. Yes the oil lines are self explanatory, just take the bolts holding the lines out and swap parts right over. Label the lines with tape if you feel like you may get them confused putting them back on. The most pain in the *** part about it is the lack of space, it took me about 2 hours and a extra set of hands to do the swap. The mounting bolts are the only hard part. Switch over the lines after you remove it from the engine. The part is located on the passenger side towards the front of the engine. I think I removed some things topside to help me but did most of the work from underneath. Good luck. It was a fun car but my best times with it was when I bought it and then when I sold it bc it gave me so many problems! If youíre in the New England area or another area thatís treated with salt due to snow check out your oil cooler lines as they have issues where they rot out. Best of luck
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