Just started couple days ago

GP lite comes on after 2-3 second delay when turn key to correct position.
Car starts

Yesterday-- GP never came on after 2 starts as mentioned above ( GP Delay)
Car would not start or even crank... as if zero battery

after several trys-over 20 minutes... w no GP lite coming on ,,, finally -delay GP lite- and start. Red battery symbol /visit workshop appeared.

drove home and turned key-- no GP lite/no start.

Started car next am on 2nd try ( 1st try no gp lite)... Battery was 12.3V prior to start... tested while running... held steady 14.0 V at idle.
Tested aux battery after 10 minutes idle... 13.0 V

ANY ideas out there??? Anyone experience the NO GP lite?

FYI- replaced both batteries and all Glow plugs within last 13 months

On the surface it sounds like the Ignition Switch and or if it was my year and model the Steering Column Lock that is between the Lock Tumbler and Ignition Switch. Don't know what setup yours has.

Don't know if it is possible for the lock tumbler to do what you describe.

How to get some idea what the issue is. Use the volt meter on the Battery and see what happens when the key is turned to the GP position and see the voltage. If there is not a voltage drop your GP relay may not be getting voltage to work.
Do the same volt meter test on the glow plug relay connector to see if it is getting voltage.
When my GP relay strip fuse cracked for a bit, I got intermittent glow plugs.

You can do the same with the wire going from the Ignition, neutral safety switch to the starter solenoid and see if it is getting voltage. No voltage at the Starter can mean the Ignition Switch and or the Neutral Safety Switch.

If you got under the Car and disconnected the neutral safety switch and identified the terminal that supplies the voltage and probe that to ground through you voltmeter, I think you could tell if it is the ignition switch/steering column lock.

Sadly, things are often a system of components and any one of the components or more can bring down the system. Sometimes you have to trace the electrical circuit back from the problem to find out where the next component that could be a problem is.

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84 300D, 82 Volvo 244Gl Diesel

What codes have been stored?

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

That 2005 has the 722.6. The neutral safety switch is integrated into the shift module. On the earlier .6s without the trip-tronic, you can remove the shifter assembly and replace the selector switch. I'm not sure if you can get the part for the later ones. To the OP. Make sure that you can see the gear selection on the instrument cluster. Everything on that system is on the CAN bus. Easy to diagnose with the right scanner. Xentry (SDS). You need to plug in to see if the shift module is communicating with the transmission to the starter or if the EIS is working properly.

fogort to mention- during these no GP/no Crank... I got the ESP and ABS error messages- with the Red battery.

LOL- after about 20 attempted starts-- NO GP lites/ still no crank...

I removed the Cover on the SAM and tapped /jiggled couple of the relays/ inspected the fuses. Still no start... came back about an hour later and got the GP lite/started!!!

Then I drove it to my Mech shop to drop off for him to inspect Monday... during the drive- confirmed- the 14.0 V with car computer. I had idea that w/ my luck the symptoms- would b gone for my mechanic... sure enough car started several times in a row... BUT both ABS and ESP lites/error messages were GONE.

I spent alot of day searching for MB owners who had similar issues
found a guy who shot video on YT - w exact conditions... he removed 1" square relay in the SAM board- used jumped back/to front post from this 4 prong relay... and got the GP lite/ and car to start?

His conclusion was a short in SAM- sent it to get rebuild... but could use jumper short term.

any ideas?

Stopped by car again... started normally.

BOTH ABS/ESP messages still gone??? How did Messages disappear on their own???

How does that happen? Where does it point to- regarding where real fault is???

Sounds like something going on with battery/starting connections to me. I'd suggest checking connections at the battery and where they terminate leaving battery. Was the battery you put in it the highest quality battery you could find? Make sure all the ground points are secure.

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Jim