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CEL - P1691 Check Engine MIL & Remote locking/unlocking working intermittently

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Hi All, I am a first time poster dealing with a couple of issues with my 99 986 that I am not sure if they could be related or not.


1. CEL P1691 error code, based on everything I have read on this board and others this is usually a burned out or malfunctioning light but in my case the light is on which is how I knew to use the code reader and got the P1691 code. Any assistance on what I can do to diagnose this would be appreciated. Note vehicle recently came out of hibernation and light came on during first day of driving. Only work done prior to driving was oil and filter change and vehicle otherwise seems fine.

2. Day one of driving this season the key head remote was working fine on day one but day two of driving it works intermittently to lock or unlock the doors, when the button is pushed the red light on the remote is activated and the rear truck button seems to work fine.

Any suggestions or advise on these two issues would be greatly appreciated.

Thanks

Sean
P1691 Malfunction Indication Light (MIL), Check engine - Interruption

indicates an interruption of power from the DME to the instrument cluster
Thanks Boxsterra any suggestion on what to check re the DME, would it be a loose or damaged wire or could it be a relay going?
Check the battery first. It also could be the CEL bulb being burnt out (just turn on the ignition without starting the car and see if it illuminates).

After that there could be rodent damage or if someone has worked on the cluster or DME areas then they probably didn't connect it back right. Make sure the DME plug in the rear trunk is properly seated and latched. Sometimes the gasket gets bunched up and messes with the connections.
Thanks Boxsterra and MarcW for the advice.

Just to give an update on my above issues.

The remote seems to be work consistently now, I didn't do anything other than open the case and put it back on. I will say that a specific section (left side) of the button seems to work but pushing the button elsewhere does not seem to work. I am going to assume the internal micro button may be going or could have a loose connection. I will be taking this apart in the next couple of days and see if it needs to be soldered. Note my backup remote stopped working a few years ago, I took it apart over this past weekend and it appears that the micro button needs to be re-soldered on it so I will attempt to repair this one at the same time.

In terms of the CEL P1691 error code. As mentioned my CEL was on which is how I knew to check the code in the first pace. I cleared the light, and it came back on. As suggested I check the connection to the DME and inspected the wiring for any sign of damage, as well as checked for any sign of rodents throughout the engine, rear trunk and elsewhere and could not identify any issue. Went for a drive yesterday and noticed the CEL was not on. I stopped, turned off the car and than turned the key on without starting it to check the instrument lights and the CEL is not coming on during the test stage. So now I am wondering if the P1691 was due to a CEL that was burning out and now it is burned out? I guess the only way to be sure is to replace the bulb. Can anyone advise what bulb I would need for my 99 986?



Edited 1 time(s). Last edit at 06/18/2019 08:12PM by scallahan. (view changes)
Here
Boxsterra - 0 months ago
Quote
scallahan
Hi All, I am a first time poster dealing with a couple of issues with my 99 986 that I am not sure if they could be related or not.


1. CEL P1691 error code, based on everything I have read on this board and others this is usually a burned out or malfunctioning light but in my case the light is on which is how I knew to use the code reader and got the P1691 code. Any assistance on what I can do to diagnose this would be appreciated. Note vehicle recently came out of hibernation and light came on during first day of driving. Only work done prior to driving was oil and filter change and vehicle otherwise seems fine.

2. Day one of driving this season the key head remote was working fine on day one but day two of driving it works intermittently to lock or unlock the doors, when the button is pushed the red light on the remote is activated and the rear truck button seems to work fine.

Any suggestions or advise on these two issues would be greatly appreciated.

Thanks

Sean

P1691: MIL Interruption in wiring.

Check wiring from ECM to instrument cluster for continuity.

Based on my experience with an always on airbag warning light the ECM has lost control of the in this case the MIL (or CEL). The failure mode of the warning light (and other warning lights) is to fail illuminated. To turn off the light the ECM has to command another chip to raise an output pin signal which interrupts the ground to the circuit it controls -- and in this case the MIL circuit -- and interrupting the ground extinguishes the light.

In the case of my Boxster the tech borrowed a cluster from another car -- with the owner's permission -- and connected it to my car just to confirm airbag warning light was off and the problem was not with the wiring from the engine controller to the cluster.

I would not be me if I didn't note the fact the car is manifesting odd electrical behavior -- the P1691 error and the key module/door lock/unlock operation -- after coming out of hibernation. This type of behavior out of the blue can be a sign rodents/mice have been at the car's electrical wiring. However, door behavior can be due to a failing door lock controller or possibly a bad door membrane that lets water from the dry side into the wet side. A check of the door bottoms after a wash or the car being exposed to rain for any signs of dampness is called for. Any dampness the door membranes -- probably in both doors -- should be replaced.

As I posted above, check the wiring from the engine controller to the instrument cluster for continuity or for anything out of the ordinary.
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