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2005 A4 Auto. A little background. New battery and new alternator. Replaced the HB in May. Had a tremendous time with the starter and had to pull the exhaust on that side to get it out.
Have my battery on a tender.
This morning I went to start the car and there was a slight hollow metalic click and nothing.
tried to start again and a lesser click and nothing. hit the stop button. after a second or 2 all the gauges light up, seat moved to position, etc. Pushed start button and it started like a champ.
Drove the car for about an hour to an appt thinking maybe I was just fat fingering the starter or something I dont know. However it ran flawlessly.
After my appt tried to start the car, same thing. hollow metalic click. then nothing. except this time it took several pushes and many more seconds of nothing then all of a sudden all the gauge lights, seat moved, etc. Push the start button all good. Except check engine light this time.
Drove the car home thinking its likely an electrical issue. Car ran flawlessly. Just the CEL.
pulled the codes and had the P0335 and P0340. been doing some searching on possible causes.
Im going to put the car up on my quick jack to check the connection to the starter and try to check the wire harness on the Cam Position Sensor. Would say a faulty crank pos sensor or starter wire cause both or would a faulty cam pos sensor or wiring cause both. Or am I looking at both as issues.
any other suggestions to check given my symptoms.
I had just driven the car the day before and there was no sign of any starting problems. This came out of nowhere.
I have had zero noted engine symptoms (ie misfire, hesitation, etc).
Well the first thing I'd tell you is check the battery. I don't know how old it is but I'd have it checked out anyway...make sure it is fully charged to 12.66 volts if a lead acid battery. Yes, I'd get underneath and check your connections at the starter...if the B+ is clean and tight and you can get to the battery block ground above the starter I'd clean that too...that would have been best accomplished when you had the starter out...now if you hear the starter solenoid clicking and you have a DVOM place one lead on the starter housing and the other lead on the battery negative cable....now try starting the car and you should see no more than 0.5 volts on the DVOM....normally you'll see 0.2 to 0.3 volts...if you see 4 volts for instance that means that only 8.66 volts is only getting back to battery negative so the car may not start...now as far as the cam and crank sensor codes if the ECM doesn't see a signal from each sensor for a few seconds the code will set...each sensor uses a 12 volt feed, a signal and low reference ground...I'm not sure if the 12 volt supply is shared on both as they are on a C5...you need the crank sensor to start but if the cam sensor were faulty you would just have an extended crank until the ECM figures out when to fire the injectors and coils
Well the first thing I'd tell you is check the battery. I don't know how old it is but I'd have it checked out anyway...make sure it is fully charged to 12.66 volts if a lead acid battery. Yes, I'd get underneath and check your connections at the starter...if the B+ is clean and tight and you can get to the battery block ground above the starter I'd clean that too...that would have been best accomplished when you had the starter out...now if you hear the starter solenoid clicking and you have a DVOM place one lead on the starter housing and the other lead on the battery negative cable....now try starting the car and you should see no more than 0.5 volts on the DVOM....normally you'll see 0.2 to 0.3 volts...if you see 4 volts for instance that means that only 8.66 volts is only getting back to battery negative so the car may not start...now as far as the cam and crank sensor codes if the ECM doesn't see a signal from each sensor for a few seconds the code will set...each sensor uses a 12 volt feed, a signal and low reference ground...I'm not sure if the 12 volt supply is shared on both as they are on a C5...you need the crank sensor to start but if the cam sensor were faulty you would just have an extended crank until the ECM figures out when to fire the injectors and coils
thanks ill check all this out. Including battery voltage even though it's only a couple months old. I think you answered one of my questions, the car doesn't crank at all. There is a slight click and completely nothing. So I'll start at the starter connections then the crank sensor.
it's too cold out right now but I'll get on it. Fortunately it's not my daily driver and can sit up on the lift for a time.
I just hope I don't have an ecm issue.
thanks I must've misread your original response.
As an update I tried yo start the car this morning and still got nothing. I then held the start button in longer and it started.
rough but started. CEL lit.
Turned it off and on again same thing, held button finally started. Rougher but started. CEL.
Borrowed neighbors hand held jumper. Started right up no issue. No delay. Perfect start. No CEL.
going to check battery connections everywhere and I guess load check battery although it's new.
Like I mentioned if you don’t want to do the voltage drop check just clean the battery terminals and at the starter solenoid and engine block…if you have a jumper cable you can hook one end to the engine block somewhere clean and the other end to battery negative and see if the car starts consistently…and check that battery !!!
Like I mentioned if you don’t want to do the voltage drop check just clean the battery terminals and at the starter solenoid and engine block…if you have a jumper cable you can hook one end to the engine block somewhere clean and the other end to battery negative and see if the car starts consistently…and check that battery !!!
so this morning I went out and took the battery out. cleaned the 2 grounds that are under the battery holder. cleaned the battery leads and the cables. applied some dielectric grease to the leads and put it all back together.
I should mention I also checked the battery voltage while it was disconnected and it was 12.77
I started the car right up although it was a bit sluggish on the start but it started fine. I noticed a ticking noise from the front of the engine bay and checked it out. the belt tensioner was chattering a bit and moving back and forth. the line on the tensioner aligned with the upper line on the housing. Its a new tensioner installed when I didnt the HB back in May. New belt as well. I did not change belts when I put on the new mechman alternator however, as I assumed the alternator wheel was the same size.
I got back in the car and the dash indicator was saying service charging systems and the battery volts were under 12. Im like whats next.
I got out and checked battery voltage and sure enough it was under 12.
checked alternator output from the cable to the alt housing it was 18.5 or so.
turned off the car. checked battery voltage 12.3
checked the tension of the belt and I could actually move the belt up and down between the tensioner and the HB easily.
I took the battery leads off again and cleaned them up a bit and checked the connections just to be sure.
Started the car again, which it was a wee bit sluggish again but cranked and started for sure. no noise from the tensioner but it was moving.
the dash volt reading slowly went up to 13.5 then drifted back down to 11.5.
I still have to lift the car to check the connections at the starter which still could be the issue. I suspect.
not sure where im going to look next.
thoughts.
Greg
Last edited by turnerg1; Dec 22, 2024 at 12:29 PM.
Ok, did you clean the alternator and battery positive cable at the starter solenoid ??…if the alternator output is ok checking it at the alternator but charging voltage at the battery is low you have a bad connection at the starter solenoid…did you do the voltage drop check ??..the 2 grounds under the battery tray have nothing to do with your issue !!
Ok, did you clean the alternator and battery positive cable at the starter solenoid ??…if the alternator output is ok checking it at the alternator but charging voltage at the battery is low you have a bad connection at the starter solenoid…did you do the voltage drop check ??..the 2 grounds under the battery tray have nothing to do with your issue !!
no I haven't gotten to the starter yet.
That's next on my list.
Just procrastinating to put it up on the jack and laying on the cold concrete.
Plus I'm trying to shrink my hands so I can get them up past the exhaust. Ok comedy.
I did not do the voltage drop yet. Hoping checking connections fixes my issue first.
it's a new battery so I'm hesitant to believe it's a problem but I know nothings perfect.
Thanks for the help here.
Like I mentioned hook up your voltmeter between battery negative and the engine block and then start the car…if you see over 0.5 volts the battery negative block ground is bad…around 0.2 to 0.3 is a good number.
Like I mentioned hook up your voltmeter between battery negative and the engine block and then start the car…if you see over 0.5 volts the battery negative block ground is bad…around 0.2 to 0.3 is a good number.
I found the issue.
The cable to the starter is about 3 full threads loose.
Not sure how it got that way.
Will disconnect battery to tighten.
Saw the ground to block right above starter and it looked super clean.
OHH !!😲…”looking” is not cleaning and reinstalling but do what you seem fit !!…let us know what you see now.
I'd have to take the starter out to get at it.
And I'd have to take the cat out to take out the starter.
I get your point but for now if tightening the nut gets everything back to normal I'll be good.
maybe one day if I have to replace starter I'll clean it.
Well just tighten the nut…if you connect one lead of your DVOM on battery negative and the other lead on preferably the starter case or the engine block and run the engine you can tell if you have a voltage drop on the ground side…actually when the engine is running the alternator case has the lowest “ground potential” and not the negative battery terminal.
Well just tighten the nut…if you connect one lead of your DVOM on battery negative and the other lead on preferably the starter case or the engine block and run the engine you can tell if you have a voltage drop on the ground side…actually when the engine is running the alternator case has the lowest “ground potential” and not the negative battery terminal.
will do, thanks.
The car is on the back burner tonight so it'll be tomorrow be for I do anything.
ill report back then.
so I got the nut tightened this morning. Tried to start the car and got nothing again. Tried it 2 or 3 times and once it decided to start it was a strong start. No longer had the service charging system and battery indicator was 13.5-14. Tried to check the volt between negative terminal and block at the bolt to engine. I don't have alligator clips but best I could hold my lead on the bolt and battery was .03. Guess I'm doing something wrong.
if I need to get to the starter to clean connections that's a complete disassembly like I noted above. Will need to find me a helper to check other voltages.
Best to get these 4mm banana jack test leads with different connectors like back and piercing probes and alligator clips… hold off on the starter connections as your issue may be on the “control side” of the starting circuit…do you know how to follow a wiring diagram ??…we will check to make sure that crank relay 43 is functioning correctly…get yourself a paper clip and we will “hotwire” the starter at terminals 30 and 87 of the crank relay….since you have an auto try starting the car in neutral instead of park…also get a 12 volt test light if you don’t have one…minimum you should have to do electrical is a good DVOM, test light and that kit posted below.
Best to get these 4mm banana jack test leads with different connectors like back and piercing probes and alligator clips… hold off on the starter connections as your issue may be on the “control side” of the starting circuit…do you know how to follow a wiring diagram ??…we will check to make sure that crank relay 43 is functioning correctly…get yourself a paper clip and we will “hotwire” the starter at terminals 30 and 87 of the crank relay….since you have an auto try starting the car in neutral instead of park…also get a 12 volt test light if you don’t have one…minimum you should have to do electrical is a good DVOM, test light and that kit posted below.
I'm more mechanical but can follow the wiring diagram similar to a piping diagram.
I did just put the prime rib in the oven so won't be on this now.
I don't know what terminals 30 and 87 are but I see the wiring and the relay.
I only have a fluke no test light or clips.
Looks like your ground voltage drop was good at 0.03 volts…below is crank relay 43…arrow is facing forward.
1) with car in park or neutral jump terminals 30 and 87 with paper clip…no need to touch the start button…engine should only crank…if you do this a few times and starter cranks you don’t have an issue with the “load” side of the starting circuit.
2) now connect test light to battery negative…test light should illuminate on terminal 86 when you push the start button…if run/crank relay on the bottom of the BCM is energized the light will illuminate.
3) connect test light to battery positive…test light will illuminate when probing terminal 85.
If engine cranks consistently jumping 30 and 87 you may have a bad crank relay 43 or run/crank relay on bottom of BCM….you can try swapping crank relay with another.
P0335 and P0340 codes not starting
