Help with No Crank No Start please!

[FourRingsC6]

PROBLEM RESOLVED PLEASE DELETE

[Mattr567]

Does your CEL turn on with the key? Can you communicate with the ecu via obd?

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[FourRingsC6]

Does your CEL turn on with the key? Can you communicate with the ecu via obd?

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Yes VCDS communicates with it. I checked for water / leaks at ecu box and all is well.


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[cactus_cars]

Does your CEL turn on with the key? Can you communicate with the ecu via obd?

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Does your CEL come on with the key?, along with the other lights like ABS / BRAKE? I feel like we are missing some details here. Does the fuel pump prime?, Dash lights, etc.

Not sure if you mean yes as in VCDS works or Yes as in the CEL comes on for Key Pos. 2.


Also I would 100% investigate the aftermarket radio just to be sure they haven't tapped into any important circuits. Maybe they tapped into a key-on circuit?

[Mattr567]

Aftermarket radio stuff usually messes with k-line communication, not something basic like cranking. But just unplugging it isn't a bad "why not" step. You can communicate with obd means the k-line isn't down.

The fact that the key turn turns on cel and can communicate is a great sign. The ignition switch is working at the very least in that regard and likely fully.

I assumed the other bulb check bulbs turn on. Does the starter even try and click at all? Have someone probe the starter while another twists the key to see if it receives voltage. Let's not get too far ahead in electrical diagrams that it might just be a locked up motor! Have to start probing at the end of the line and work your way back if no power is found.

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[FourRingsC6]

Aftermarket radio stuff usually messes with k-line communication, not something basic like cranking. But just unplugging it isn't a bad "why not" step. You can communicate with obd means the k-line isn't down.

The fact that the key turn turns on cel and can communicate is a great sign. The ignition switch is working at the very least in that regard and likely fully.

I assumed the other bulb check bulbs turn on. Does the starter even try and click at all? Have someone probe the starter while another twists the key to see if it receives voltage. Let's not get too far ahead in electrical diagrams that it might just be a locked up motor! Have to start probing at the end of the line and work your way back if no power is found.

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When key is turned there is no clicking from starter solenoid.
I’m going to see today if i’m getting power to signal wire that goes to the starter.
I checked continuity and wire is good from starter to ECU box. From ECU box to under dash was not tested yet.
Ignition switch was tested and getting power.



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[FourRingsC6]

I was able to print diagram from prodemand so hoping it will help me looking for what i need




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[walky_talky20]

So we aren't getting any Starter Activity at all? Engine will not rotate?

Lucky for you, the starter circuit is the simplest circuit on the entire car! Let's fix it.

- There IS a starter relay. This is for the clutch start safety (if equipped) and the Security System (can interrupt the starter signal wire during an active alarm event)
- You can absolutely bypass the starter relay. This will connect the START output of the ignition switch directly to the Starter Solenoid (Very direct. No fuses, no relays, no Safety of any kind).

Diagnosis of B5 A4 "no crank" is an easy 8 step process (LOL):
1. Ideally you would check for power at the Starter Motor (hot at all times, direct to the battery), and power at the Starter Solenoid (hot only while key is held in START position, need 2 people for this)
2. B5 A4 starter is kind of hard to get to (cannot reach from above), so the Next Best place to start diagnosing things is the Starter Relay
3. Starter Relay has 4 pins: 2 of them are 12v+ from the START position of the key, 1 is ground from the Security System (also goes through clutch safety switch, if equipped), and lastly the output wire to the Starter Solenoid.
4. You can yank the relay out and just test that you have 2 pins with the START signal and 1 pin with a ground (may need clutch depressed to see ground!)
5. Obviously if you are missing the ground, your problem is MISSING GROUND TO RELAY. If you don't have 12v+ signal from the Key (x2), then your problem is MISSING 12v+ START SIGNAL.
6. If those 3 pins check out perfectly, then as a final test you can APPLY 12v+ to the 4th pin (the pin that is the output to the starter).
NOTE: This is extremely dangerous. You are bypassing all safeties. Make sure car is not in gear. It will crank the engine and immediately run over and kill everything in it's path if you leave it in gear during this test.
7. If sending power directly to the output pin does not engage the starter, then you have ISSUES AFTER STARTER RELAY.
8. If sending power direct to the output pin, did crank the engine, (and everything in Step 6 checked out OK) then you may just have a faulty relay.

MISSING GROUND TO RELAY
- You can fix the problem (dude where's my ground? Security System, Clutch switch or wiring, go fix it)
- OR if you so choose, you can bypass the need for a ground and eliminate the relay altogether.
- With relay removed you can use a jumper wire to connect one of the 12v+ Start Signal pins directly to the Output Pin.
- This will bypass all safeties. Pushing clutch not required to start car. Early B5's may have been like this from the factory anyway.

MISSING 12v+ START SIGNAL.
- This is uncommon
- Are you certain you are checking the correct relay location?
- If you're sure, then you might have a bad ignition switch.

ISSUES AFTER STARTER RELAY.
- Now you need to actually get under the car and check things at your starter
- 4 things to do at the starter:
- Does my Starter Motor have battery power? (Big Wire)
- Does my Starter Motor have good ground to the starter case?
- Check continuity of the wire from starter relay to starter solenoid location (Is my starter signal wire any good?)
- If I jump battery power to the solenoid directly at the starter, does it crank? (Is my starter any good?)

**For automatic car, everything above is the same. Just substitute "Park/Neutral Safety Switch" for Clutch Switch.