Jules 75ZT

Hello from a newbie!!
Driving me nuts this one.


Symptoms of my 2003 SL55 AMG 36K Miles from new .....always garaged. Both batteries are trickle charged.

Sometimes and very randomly won't crank over (no starter relay click). It does this with both keys and keyless.

Also the display doesn't always show the gear selection ie P and W etc.

Sometimes it shows incorrect gear!

It happens wether hot or cold and happens when it's just been driven 5 mins ago or not used for a week.

Both batteries new.

Green starter relay L changed

Other relays are heard in engine bay

Fuel pump and ABS always primes as normal.

I've fitted the uprated metal lever to ESM but occasionally the park solenoid doesn't always operate when brake pedal pressed. (even though brake lights come on every time)

It seems to do different things every time ignition switched on !!

Front and rear SAM modules have been removed to check for corrosion but both look new.

I have LAUNCH OBD diagnostics which talks to all the modules fine.

The only fault showing is P1925 which means Drive Authorisation has been refused by N15/5 ESM gear select module. (same with both keys)

Both connectors on the ESM were spotless but cleaned anyway. (no coffee spilt down it etc)

I suspect the PCB module itself but it doesn't seem a common fault at all. Most ESM issues are the usual mechanical stuck in Park caused by the black plastic lever.

My next plan is to get a Virgin ESM and get it programmed to the car.

Lately it got worse in that it may take 20 attempts of ignition off & key out to get it to crank over. Once she does run everything is perfect.

Any other ideas guys?

Please read carefully so you don't suggest things I've already tried above.

Nor Cal SL55

Sounds like crankshaft position sensor...?

Jules 75ZT

BUT it would still crank but not start if that sensor was faulty.
Also no fault code in ECM memory.

blueSL

Wondering where you got up with this. My car has started doing similar, typically in the morning, I hear a relay click but the engine doesn’t turn over. Leave it a few seconds and, so far, it starts. I’m wondering whether the starter battery is bad, the car is 17 years old and it’s never been replaced.

Jules 75ZT

Still on my ramp !!!
Your relay clicking is different to my fault. (no clicking of relay L green starter relay)

Measure the voltage during cranking.
If it's going below 9v replace battery.
After 17 years maybe replace it anyway !!

However if your battery was bad it wouldn't then recover itself to start the after it's just clicked a few times.

Sounds like your starter solenoid or relay L itself.
You can bridge relay L output contacts to prove this if you are competent to do that which will narrow things down a bit.

Good luck