'99 Nissan Quest P0105-P0325-P1605-P0446-P1400-P1705 andmore

hardwire that circuit directly from the pcm to that sensor!

Thank you Jeff for your reply. The Absolute Pressure Sensor wiring diagram is the following: I will hardwire the circuit as per your suggestion. Should I hardwire all the circuit shown above or if wire between 3-42 will do the trick at this point? That you again. Hugo

You may have already found the problem since your post is from a couple of weeks ago but, check your fuses in the fuse panel inside the vehicle under the dash on the drivers side(left). There should be a 10A fuse at location #4. This fuse feeds power to the items that are triggering the codes that you mentioned. If the fuse is blown try puting in a new one to see if it solves your problems. Keep in mind that if the new fuse doesn't blow out then there may be an intermittent problem and the fuse could blow again at anytime. If the fuse blows immediately then there is a short in the wiring or one of the components that the fuse feeds power to. If there is a short in the circuit you will need to find the cause. I would suggest that you unplug all of the components that the fuse sends power to then install a new fuse to see if it still blows. Finding and unplugging all of the components could take some time so, don't expect this to be a quick 5 minute job. If the fuse blows out with all of the components disconnected it indicates that there is a short in the wiring (provided that you are sure that you disconnected all of the components that the fuse feeds). Finding a short in the wiring is something I would leave to a pro if your not familiar with the process. Good Luck!!

Hello chasr212r, No, unfortunately, I have not found the problem yet. I do not travel with the car. I will check again the fuses as per your suggestion and will check carefully the fuse at location #4. I am not sure if this is a problem with the ECM itself and doesn't know how to figure out. Thanks for your input. Best

chasr212r, I have check the fuse #4 (10A, engine control) and it is not blown. I have took out this fuse and couldn't start the car. So this fuse need to be in there and good. Any others suggestions are welcome. Thanks.

so do you have 5 volts coming out of the pcm on pin 42? and verify that the voltage to pin 43 of the pcm and 42 of the tcm are the same, if not I'd be checking that splice. If you have 5 volts coming from the pcm but it's not making it to the sensor then before tearing open the harness try running a new wire from the pcm connector to the sensor connector!

I think I jumped ahead of myself on my last recommendation to check fuse #4. It feeds power to several items but I didn't read into your problem well enough to make a good responce. I haven't found a schematic to help look for the common circuitry to your problem but I think Jeff is on the right track. You may want to start from scratch and pick one of the sensor circuits to test . Look for your 5 volt reference voltage at the sensor. If you don't have the 5 volt signal at the sensor then go right to the computer terminal to see if you have it there. If the 5 volt signal is o.k. at the computer then it is time to look for a problem in the wiring, perhaps a connector problem or a faulty splice? Keep us informed!

Hello Jeff and chasr212r and thank you both for your input. Today is a great day to work outside... on my car. I've just checked voltage (in regard of Nissan Quest 1999 Service Manual): 1. Voltage between ECM terminal 45 (ABS pressure sensor signal) and ground is 0.29V which should be > 1.74V. 2. Voltage between ECM terminal 42 and ground is 0.4V which should be 5V. I've check ground circuit between harness terminal 1 and engine ground and continuity exist as it should. 3. I've also checked harness for short to power (terminal 3) and continuity exist to engine ground and also to harness terminal 1. Below is a scan of the DTC P0105 Absolute Pressure Sensor wiring diagram: I am a little bit confused. Should I conclude that the ECM is faulty? How can I determine that ECM is faulty and if so how can I check a faulty ECM? What should I check next? Thanks for your advice and input you may be able to give. Sincerely,

If the manual says there is to be 5 volts at that pin of the pcm and there isn't then likely it is bad although Im not sure how common pcm failures are on nissans. If you're unsure of your diagnosis, get a 2nd opinion about the circuit before throwing alot of parts and money at it that it doesn't need. In the end it's sometimes the best way!

I would have to agree with Jeff on this one. If there is no 5 volt signal from the ECM I would say the ECM is faulty. It's not common but I have replace several ECMs on Nissan over the years. I have seen them with corrosion on the circuit board and I've also seen burnt sections as well as faulty solder connections. Based on the information you have provided I would say replacement of the ECM would be the best bet at this point. It's difficult to make a good diagnosis on a problem like this without seeing the vehicle, but I believe you need to trust your test results and make your next move. Best of Luck!!

Thank you very much Jeff and chasr212r for your valuable help. I would like you to give me your thoughts on this: I've taken my car for road test and for a minute or two the car behaved normally, except for the abnormal shifting, but rpm wasn't fluctuating and I was able to drive at 3000 and more rpm. Otherwise rpm doesn't exceed 3000 rpm! Is this trouble another indication of a faulty ECM? Thank you again.

not necessarily, you need to committ to replacing the pcm or seek professional diag at this point! A scan tool is not the cure all for every scenario out there! Almost any sympton has the potential to be caused by a pcm malfuction but pcms are often extremely pricey to try and deter people from shotgun diagnosis using new pcms, Bad wiring, bad sensors etc can all cause these scenarios but a good tech with a good scan tool and a wiring diagram should be able to pinpoint it, you are gonna have to bite the bullet and leave it to the professionals on this one! Good luck and let us know how you make out!

Jeff, One thing I could try is to remove the ECM from the car and supply correct voltage and check voltage at AVCC terminal 42 (should be 5V otherwise ECM is faulty). Is this a good test? I've just called a Nissan dealer and they told me that ECM is 1099.99$ CAN. Wow.

no it's not a good test! if there's supposed to be 5 volts out of the pcm connector and there isn't and you're reading the circuit properly then removing the pcm and and putting 5 volts down that wire will be pointless! If there is no signifigant voltage drop down that wire and there is no voltage coming the pcm then it kinda points to itself!

Jeff, I would like to give another try. What about erasing ECM memory? And restart troubleshooting. Instead of removing ECM from the car I will disconnect sensor harness and check voltage at ECM pin 42 and ground. I worry about the 5V for power supply to the sensor...

I'd have a good mechanic check it at this point! 2 or 3 hrs diag time is better spent to confirm your suspicion then spending a thoudand dollars on a pcm that it doesn't require! don't be too proud to admit that something is beyond your abilities! Without the vehicle in frt of me it might very well beyond mine at this point!

The ECM has a internal regulator to provide a constant/controlled 5 volts output voltage feed for the sensors. If the 5 volt signal is bad then there is an internal computer problem, provided that the computer has its normal 12volt inputs and good grounds. Have you considered trying a used ECM?? I work on a lot of Nissans and rarely come across a bad ECM (although I have replaced a few) so I would be inclined to try a used one rather than a new one at the price you were quoted. I could give you some sources for a used part if you would like to give it a try. I don't know if I can give the information to you here, but I could email it to you if you want?? Keep in mind that I only make the recommendation to replaced the ECM based on the information you have supplied. Let me know what you think??