2014 Q7 TDI flashing glow plug light and won't crank engine

[chubb]

Hi Everyone,

This problem just started about a week ago. When I try to start my Q7 it won't crank the engine and all I see is a flashing glow plug light. I tried starting it with the push button start and by turning the key - same result.

At first I thought it was a dead battery issue because a did hear a few clicks SOMETIMES during my multiple attempts to crank the engine. I used my other car to jump start it and after leaving them both connected for awhile...maybe 5 minutes I was able to get the Q7 started with multiple crank attempts.

When i got home I tested the alternator to verify it's charging the battery, and it definitely is. I also checked the battery voltage and it is fine as well. I also checked the battery voltage when turning the ignition key and the voltage doesn't drop much like it would if the battery was shot - Keep in mind it doesn't engage the starter motor. I'm confident it's not the battery and alternator.

I have the ross tech cable and software. The trouble code indicated bad or stuck starter. Normally I would just assume its a bad starter but I just want to make sure I'm not overlooking anything else like a bad starter relay or glow plug relay module - I think the flashing glow plug light is making me question if it's the actual starter motor or not. The starter motor is expensive and NOT easy to replace so I don't want to do it unless I'm 100% sure that's the problem.

does anyone know how to properly trouble shoot the starting circuit? I have no service manual or wiring diagram - can't find ANY info online.

What's the purpose of the glow plug relay p/n 4L0907282A - could it be bad and prevent the starter from cranking? is there a way to test this thing?

I have been able to get it started sometimes - usually in the morning after it's been on a trickle charger overnight. Again i don't think it's the battery as the voltage is easily around 13 volts and really doesn't drop when attempting to start the car. At this point I cant get it to crank no matter what I do - battery fully charged, jump starting, etc... just shows flashing glow light, no crank, and trouble code motor bad or stuck.

Any help would be very much appreciated.

cheers!

[s4buckeye]

How many miles? Any other symptoms prior to that?


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[Audibot]

Flashing glow plug light would indicate a malfunction in that system. Glow plug relay should be the control relay that flows current (and hence heats) the glow plugs. Appears to be an interlock by Audi preventing starting the car without functioning glow plugs.

Have you pulled the relay? Wondering if any of the spades are burnt (indicating an issue). Also check your fuses just in case.

Being able to start it overnight after it's been trickle charging suggests the relay itself may be bad and only when it's cold does it function correctly (ironically, your engine is probably warm enough to start w/o the glow plugs).

[chubb]

My Q7 has about 140,000 miles on it. the only other problem I had with it was a significant coolant leak caused by the oil cooler under the intake manifold. I just finished fixing this particular issue. I was able to start and drive the car after this repair so I don't think my coolant problem caused this problem since my starting issue was there BEFORE i fixed the oil cooler issue and the car started fine AFTER the repair. after I deal with my car starting issues, I'll post about this ordeal to help others that are having mystery low coolant problem.


Yes I pulled the glow plug relay thinking I could test it like a normal relay but that doesn't seem to be the case - I think it does more than a normal relay. The glow plug relay looks fine - no physical evidence of a problem with it.

yes I agree that temp may affect the relay and it works when cold. As you said it's funny that I only have the issue once the engine is hot from running and the glow plugs aren't needed...well up until yesterday...now the thing won't start cold or hot. that said, it's been in my garage since i was dealing with repairing the oil cooler issue above when normally it would be parked outside in the freezing cold.

if the was the glow plug relay shouldn't there be a code to indicate this and picked up by vcds?

[s4buckeye]

i had intermittent glow plug light issues, but start up was not an issue

was at 80k miles, was the EGR flap/valve sticking. EGR was filthy and it took the dealer forever to fix it

anyway, mine was covered under the dieselgate warranty to 120k, but maybe yours is covered under the longer emissions warranty?



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[chubb]

i had intermittent glow plug light issues, but start up was not an issue

was at 80k miles, was the EGR flap/valve sticking. EGR was filthy and it took the dealer forever to fix it

anyway, mine was covered under the dieselgate warranty to 120k, but maybe yours is covered under the longer emissions warranty?



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I think if it was an EGR flap, it would trip a code indicating EGR system failure.

that said, I know EXACTLY what you mean by filthy EGR!. Because i just finished fixing a big coolant leak with my oil cooler - I had to disassembly the intake manifold, inlet tube, and a bunch of other stuff. The intake tube and intake manifold was nasty!!! I'm surprised my Q7 was running as well as it did (well when it starts that is .... ) so much for clean diesel - yikes.

I don't think this issue has anything to do with my no start, no crank. After I fixed the coolant leak issue I was able to start the car and drive it at least twice - ran GREAT!

if you want to see what I mean by coolant leak at oil cooler - go to youtube and search for "2013 Audi Q7 3.0 TDI bad coolant leak Part 1". my issue was identically to what you see in this video. My EGR and intake tube was even more clogged than his.

[chubb]

-Solved- My flashing glow plug light and no crank/start issue.

After a lot of trouble shooting, head scratching, and misdiagnosis - I finally figured out what was causing my no crank issue....

1. First...I have no idea why an Audi engineer thought this was a good thing to do, but a flashing glow plug light can be VERY misleading - this of course lead me to replace my glow plug module which didn't solve the problem and was a complete waste of 100 bucks :(

According to the manual a flashing glow plug light indicates a system malfunction. Because my Q7 wouldn't start and VCDS picked up numerous glow plug failure codes that weren't there initially but eventually showed up, I thought the module failed and prevented the ECM from sending the starter signal.....wrong. Because I had issues starting my car, I stopped using the start/stop push button and instead used the key in the ignition switch when attempting to start my car over, and over, and over again. I did this because i thought there may be an issue with the push button and thus it wasn't sending the start signal. Since I never use the manual ignition switch, I was confident that it was working fine and gave me better control over starting my car, cranking time, repeating cranking attempts, etc. Here's what I didn't know or realize until now and what's stupid and misleading....when you turn the key to the ON position (and leave it there...don't crank) your entire electrical system gets power and the glow plugs fire up. The glow plug light will light solid for 1-2 seconds as you would expect, but after that the light starts flashing for no apparent reason. Of course normally you'd never leave your key and this position and continue to the crank position to start the car. Assuming it starts the engine, the glow plug light turns off and doesn't start flashing. Who at Audi thought it was a good idea to flash the glow plug light if the operator moves the key to the on position and just leaves it there?????

Moving on - the real issue why my car wouldn't start and why I was getting glow plug codes was due to a bad ground cable. There's a ground cable to the left of the alternator and under the air filter box. you can only see it from from under the car - you can't see it looking down through the engine compartment. This cable connects the frame to the passenger side motor mount. Right from the beginning I checked this cable, even disconnected it to clean the attachment points with a wire brush. Turns out this cable was faulty and corroded inside. To me it looks like this cable wasn't manufactured properly and the cable housing didn't form/mold correctly (I'm sure it was like this right from the factory). It doesn't look split, just looks poorly molded. As a result water/salt got in over the years and corroded the inside thus preventing proper voltage at the starter and bad ground for the glow plugs in the engine block (that explains the glow plug codes i found with VCDS). Unbelievably, the split was on the top side of the cable and completely invisible when looking at it from under the car! even though the split extends the length of the cable and spirals around it partly - the split totally faced up towards the engine compartment. Since the cable looked fine the split was totally missed, I moved on with my trouble-shooting.

OK....normally you'd measure the voltage at the starter motor during cranking when trouble shooting such issues but the starter and the electrical connections are impossible to get to! you'd need to remove, the alternator, engine mount, inter cooler air tubes, etc... it's a very big job so that wasn't an option at this point.

So how I did it finally figured this out? Well, I ran out of options and figured the starter motor was shot or at least was going to take measurement directly from it. I began to disassemble everything needed to get to it. lucky for me i started with removing the engine air filter box. This exposed the grounding cable when looking down through the engine compartment and i could now see the top side of the cable thus exposing the split :)

Long story short:

1. Carefully and fully inspect suspect components for problems.
2. Don't ignore seemingly small voltage drops when trouble shooting possible ground issues or connection issues. Right from the beginning I detected a very small voltage difference from one end of the bad ground cable to the other, which is the reason why I cleaned the attachment points...unfortunately I didn't follow point #1.


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