Hard start, then crank with no start, then no crank...

[peterbillygrace]

Hi everyone,

I'm having a bad night and I'm looking for some help diagnosing a no start issue. The sequence of events were:

1) Girlfriend texts to say the car sounds like isn't going to start, but then starts.
2) Girlfriend gets home and I try to start the car and it fires up no probem.
3) I decide to break out the eBay cable and VCDS lite anyway and get the following codes.

VCDS-Lite Version: Release 1.2
Wednesday, 17 August 2016, 18:50:08.


Chassis Type: 8E - Audi A4 B6
Scan: 01,02,03,08,09,0F,11,15,16,17,18,36,37,45,46,55,56 ,57,65,67,69,75,76,77

-------------------------------------------------------------------------------
Address 01: Engine Labels: Redir Fail!
Controller: 8E0 909 518 BC
Component: 1.8L R4/5VT G 0030
Coding: 0016751
Shop #: WSC 91445
VCID: 729759CB2DB7
3 Faults Found:
17700 - Map Controlled Engine Cooling Thermostat (F265): Open Circuit
P1292 - 004 - No Signal/Communication - Intermittent
16840 - Shareware Version. To Decode all DTCs
P0456 - 001 - Please Register/Activate - Intermittent
16395 - Shareware Version. To Decode all DTCs
P0011 - 008 - Please Register/Activate - Intermittent
Readiness: 0000 0000

-------------------------------------------------------------------------------
Address 02: Auto Trans Labels: 01V-927-156.LBL
Controller: 8E0 927 156 AA
Component: AG5 01V 1.8l5VT USA 0505
Coding: 0001002
Shop #: WSC 06335
VCID: 6DAD4AB73489
No fault code found.

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 8E0-614-517.LBL
Controller: 8E0 614 517 A
Component: ABS/ESP allrad 4529
Coding: 04277
Shop #: WSC 06435
VCID: 263F759BD1FF
No fault code found.

4) I curse, do some Googling and decide to start with the timing belt since I just changed it a few hundred KM's ago.
5) Timing belt still looks brand new and the tensioner gap is still at 8mm with an Allen key feeler.
6) I knock on the cam position sensor a few times and start it again with no problem.
7) I decide to clear the codes in case they are left over from the TB job and things get worse....crank but no start.
8) Check for new codes:

VCDS-Lite Version: Release 1.2
Wednesday, 17 August 2016, 20:15:59.
Control Module Part Number: 8E0 909 518 BC
Component and/or Version: 1.8L R4/5VT G 0030
Software Coding: 0016751
Work Shop Code: WSC 91445
VCID: 729759CB2DB7
1 Fault Found:
17072 - ECM Power Relay Load Circuit: (J271): Open Circuit
P0688 - 004 - No Signal/Communication

9) Curse some more and send the GF for pizza and beer.
10) Check all the drivers door fuses, none blown.
11) Decide to try and clear the new code and then get no crank...just some flashing dash lights and sounds under the dash. The 17072 code comes right back.
12) Do some more googling and pull the kick panel to look for water or burnt things *the car was parked outside last night in heavy rain and it usually lives in the garage*
13) Pull the negative battery cable for a few minutes and try try to start again, still no crank.
14) Start to open the ECU box and crack the windshield as I'm trying to pull up the drivers wiper...awesome. It looks like there was a rock chip just at the trim.
15) Get into the ECU box and everything looks dry, the 2 fuses I can see are ok.
16) Started to pull the ECU to try and find the J271 relay when the GF got back with food.

Right now it's sitting with the negative battery cable unplugged and I just have the weird plastic bracket under the ECU to pull and I'm hoping I'll then find the J271? Does it sound like I'm on the right track, or has the Internet led me down a rabbit hole?

The only work I've done recently was the $50 O2 sensor swap on Sunday and it ran well Monday and Tuesday. All the splices were soldered and had hest shrink on them.

Oh, it's a 2005 A4 1.8t with just over 200,000 km's. Any advise or input is apreciated, TIA.

[Let it snow]

If the engine won't crank/turn at all first start with the basics. Check your battery terminals and ground. Then check the standing voltage and then the voltage when you try to start the car. Also what happens when you try to start it? Any starter noises? The ECU relay does not stop the engine from cranking.

[diagnosticator]

Make sure the battery is fully charged.

[peterbillygrace]

The battery was run almost completely down, it's on the charger now. I didn't even consider that it would die so quickly!

While I was putting everything back together I cleaned the battery and coil pack grounds, and checked the coil pack wires near the connectors, they are hard but not burnt or cracked. I also checked the relays below the ECU since I was there and nothing looked damaged.

There were a ton of pine needles plugging both drains below the battery/brake booster so I cleaned that all out as well. It was still pretty wet from the rain.

I'll see what happens when I get the charged battery back in later tonight.

[Charles.waite]

If its not the battery, then my best guess would be Crank position sensor. Those usually fail inntermittently before they just go kaput.

Of course it could be battery. I replaced my battery way back because its resting voltage was around 10V. It had enough amperage to crank and turn over first time, but it would have this weird misfirey thing for a few seconds on cold starts until the Alternator could float the voltage high enough to bump it up to the normal 13V+. Only happened on cold starts and after replacing the battery it went away. Old batteries with sagging voltages can cause all sorts of bizarre issues.

[peterbillygrace]

It started up fine this morning with the freshly charged battery. I'll let it sit for a while and see if the voltage drops, and I'll probably pull the battery again to take it in to be checked.

The power relay code cleared this this morning as well, there's just a steering angle sensor code (01826) left. Hopefully that's just from me panicking and checking all the fuses. I'll try to clear it again later today after a test drive.

[peterbillygrace]

Let it sit for a few hours then checked the battery (12.6V) and tried to start it. It was back to a hard start so I took the battery to get tested. Results came back 95% life left with 688 of 690 CCA's.

Hot starts seem to be fine so I'll check the battery voltage again in the morning just to be sure it's not dropping. I also ordered a crank sensor as per Charles suggestion and I'll put it in this weekend and see if that helps.

All the codes are clear now except the thermostat.

[old guy]

You may have a defective rear coolant temperature sensor. The ECM utilizes the CTS reading to enrichen the A/F ratio during a cold start (same thing as a choke on an old school carburetor). If the ECM thinks the block is already up to temperature it won't add fuel and you get a hard start condition. Once up to temperature starts are normal.

[peterbillygrace]

Thanks OG, I'll try replacing that as well. If I remember correctly they are pretty cheap.

[Charles.waite]

Thanks OG, I'll try replacing that as well. If I remember correctly they are pretty cheap.

Yea they're like $20. I didn't think about that being the issue but it very well could be. I would do that first and see if it fixes the issue. If it does then you can just return the crank sensor.

[peterbillygrace]

Replaced the CTS today and since I was due for an oil change I put the new CPS in while I had the oil filter out. Everything went ok until I started it and it stalled out after a few seconds. I pulled the codes and the was no communication to the CPS...put the old CPS back in and it fired up right away. I'll probably still put the CPS in when I get a replacement.

When I was moving the PRV to make room to put the CTS back in I ripped a hose (it was completely melted to the metal pipe) I noticed there was a lot of carbon/ash build up, is it worth cleaning out everything from the valve cover to the intake when I replace the torn hose?