I just recently completed a cam and lifter swap, as well as received a new mail order tune from ECS. The main reason for the mail order tune was to tune out the AIR system since I removed it during these upgrades.

My car is running great, but has started randomly throwing P0103 (Mass Air Flow Circuit High Input) and P0327 (Front Knock Sensor) CEL codes at the same time. It's very random when it happens, sometimes I can drive the car 100 miles without the codes being thrown, sometimes the codes get thrown within a minute of starting the car up (usually they show up close to the time I turn the car on). If I clear the codes, they do not return while driving the car -- it seems to mostly be around startup.

I proactively replaced both knock sensors and the knock sensor wiring harness in hopes that the codes would clear up, but they did not.

Any ideas? All input is appreciated, thanks in advance.

 

As far as your knock sensors go during installation their torque is “critical” and also you can check the wiring between the sensor harness and the PCM since you had the PCM and it’s harness disconnected...addressing your P0103 I’d check the connections at the MAF especially the ground (which is a body ground)...with the MAF unplugged key ON you should see system voltage on the pink wire, 5 volts on the yellow, and a good ground !!...BTW, a continuity test on grounds are not the best way to do it...must be a “loaded”circuit test...if you have an old headlight bulb laying around that is the way to test it...if not if system voltage is 12 volts you can see what that voltage is between the pink wire and MAF ground..,should read 12 volts !!...with the MAF plugged in you should never see 5 or 0 volts on the yellow signal wire back probing that wire !!...as far as the cam/lifter swap was the an OEM going back in or a “performance” cam ??...car should have been tuned with that modification done !!

 

I torqued the knock sensors to 15 ft lbs as the service manual calls for. The codes definitely seem to be related to one another, they both get thrown at the same time. I'll see how far I can get testing the voltage, but I'm not great with electrical.

The cam is pretty mild, and COMP Cams agreed that I probably don't need a dyno tune for it. The car runs great without a tune, and the mail order tune I got from ECS seems to be sufficient. Down the road I plan to get a dyno tune, but all tuners around me are booked for months in advance.

 

unfortunately the knock sensors produce their own AC voltage and the MAF sensor isn’t tied into that circuit so both codes happening at the same time was probably a coincidence..again I can only suggest removing the PCM connectors and make sure no pins are bent and there is no corrosion present...if you are bad with electrical you can bring the car to a auto repair/electric shop !!...they may be able to help !!...GOOD LUCK !!

 

that’s really strange because the codes continuously get thrown together. Almost everytime I start the car, within a minute both codes are thrown — always together, never one by themselves.

 

If you have a multi meter and you can perform the MAF voltage and ground checks that is about the only thing I can suggest at this time !!

 

I’ve been side tracked and stopped troubleshooting this for awhile. I go to start the car tonight and a new code is present — P1637. Some forum posts suggest a bad alternator, some suggest a bad PCM. It’s fairly coincidental that I recently sent my PCM in for a mail order tune.

 

Sometimes a bad alternator can cause excess "AC Ripple" and cause all kinds of havoc in the cars electrical system especially systems that use AC...wheel speed and knock sensors...you could check this AC ripple voltage at your battery terminals and see what you have...should be less than .5 volts AC...if ripple OK see if you have 5 volts DC with the alternator harness disconnected at the RED wire (L terminal) with key ON...if OK check the harness connections...if NO 5 volts you'll have to check for opens or shorts between the red wire and the PCM. the P0103 is a MAF high frequency DTC...if your DVOM has a frequency setting you can check that...I believe if the PCM sees over 14,000 Hz for a second that DTC will set.

 

I'm starting to lean towards the alternator, although I'm still not sure where to even begin with all of the electrical goofiness. The 2 original codes, P0103 and P0327 now come on with every start. S

I tracked the car last weekend, and the car ran very well. I noticed that when the car would get hot at the end of the session, the rubber surrounding the alternator ground/connection was so hot it was melting the perimeter of the rubber and smoking a bit. The cable also appears a bit black from this. Not sure if it's relevant, but thought I'd share all details.

I let it sit for a week or so and then drove it yesterday. The car drove well, with the same 2 codes it's been throwing, until I headed home. Driving down the freeway, all of the sudden I started getting 'Service ABS' and 'Service Traction Control' messages on the DIC. I looked at the battery volts gauge and it was fluctuating from ~12v all the way down to 9v. The car at one point also get a 'Low Voltage' message and the red 'Check Gauges' light came on. I pulled off the freeway, and inspected the engine bay -- all seemed normal. I fired the car back up and drove it home without any issues, the car read 13.3-13.5v all the way home. Here are the codes I got from the DIC after this fiasco;

P0103 - usual
P0327 - usual
P1637 - new
C1236 - new
B0367 - new
B2282 - new
B2284 - new

Could it be my alternator going bad? It appears the alternator is connected right near the knock sensor harness and MAF wiring which have been throwing the codes that started this thread.

 

Could be an alternator but you can check for AC ripple with a DVOM !!...check that !!...all those DTC’s are voltage related...1637 and 1236 !!...are you familiar with using a DVOM ????

 

I'm never used a DVOM before, or even attempted to troubleshoot an electrical issue before. I'll try to source one and start learning. Power is very foreign to me. Thank you for your replies!

 

Electricity is comparable to the flow of water...with a 20 year old car that has electrical gremlins to begin with I’d sleep with your DVOM...LOL !!...some good videos !!

 

I just ordered a multimeter that should arrive tomorrow and I also pre-ordered a new alternator since my spidey sense is telling me that it's the culprit.

 

First I would suggest getting schooled on your DVOM for diagnosing then perhaps taking the car to a trusted repair /electrical auto shop...taking your old alternator to a rebuild shop is the preferred method since there are horror stories of new alternators not working properly after replacement...there is more alternator info you can read in the “sticky’s” section of the Tech Forum !!

 

those videos were super helpful and I’ll definitely be testing my alternator before installing a new one. The current alternator in the car I bought used on these forums from a member named BLOWNBLUEZ06. It had an unknown # of miles on it. When I originally bought the car it had an aftermarket alternator that was giving the “Charging System Fault” message, although it did function as desired.

I’m planning on buying an Ultima reman from OReillys with a lifetime warranty — mostly because it’s the only auto parts store near the track I go to most. If it doesn’t work or gives me issues I’ll get the current one rebuilt, but the $200 alternator will be a cheaper test than taking it to an auto shop IMO.

 

So alternator tested bad. I replaced it with an OReilly's Ultima reman and it works fine -- never drops below 14v under load and no Charging System Fault.

My original codes P0103 and P0327 are still being thrown. I spoke to ECS regarding the MAF code P0103 and they think it's due to the mail order tune -- I can fix that sometime down the road. The P0327 front knock sensor code is the one I want to troubleshoot.

Now that I have my multimeter, how should I tackle the P0327 code?

 

The P0327 is the front knock sensor so if you replaced the sensors and harnesses already without having to access Connector C112 again behind the intake manifold I'd backprobe the wire at the PCM using T-pins (pictured and you can pick them up at a craft store or use a sharp needle) and see if you have some "AC" voltage (less than 1 volt) with the engine off and probing Pin 51 (dark blue wire) at the PCM C1 connector...you may have some wiring issues between the replaced harness and the PCM where the wire terminates at !!...there are 2 connectors at the PCM...C1 and C2...you will have to pop off the gray cover to backprobe the wires...if you squeeze the ends and pull down the cover it should release on that end (pictured)...be careful or you may break the 2 tabs on each end...with the DVOM set on a low scale like 2 volts with AC selected tap on the engine block as in the video and see if you read something...the other sensor wire is a light blue wire at Pin 11 on the same PCM connector...if you don't feel comfortable doing this I'd suggest taking the car to a shop that does electrical work !!...I'd erase the 0327 code and see if it comes back when the engine is started but before you turn the engine OFF and see if it shows as a "C" or current code...it should NOT because the engine has to be warm, engine RPM between 2-3 thousand and above idle !!