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Discussion Starter · #1 ·
Hey there, just got a new Disco and am having some issues with starting and limp mode

A few days ago, car was cranking but wouldn’t start – no lights were on. After 3-4 goes it went.

Next time I tried it, it wouldn’t go at all. A day later it did but after about 10 minutes driving the S and M lights came on and it went into limp mode.

I then test battery and it was 12.3v… it looked pretty old so I bought a new one, cleaned terminals and was getting 12.8v from both terminals and leads. Car started but after 10 minutes back in limp mode…

Now when I go to start it the S and M lights come on and it cranks but won’t start.

From my Googling etc it seems to be that it could be one of a few things:
• Alternator
• Crank sensor
• Grounds
• Air box and hoses
• XYZ (but I did the rear wiper test – and that worked, though not sure if this is reliable)
• Transmission fluid
• Wastegate actuator

I know I need to use a code reader but my mate with one is away at moment. Any suggestions on easy ways of solving/ruling out any of these?

Thanks in advance!
 

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Welcome to the forum
The more specific you are, the easier it will be for others to help. You posted in the discovery 2 section which may be “new to you” but definitely isn’t “new”.
What year?
What engine?
And yes a good code reader will likely be a strong investment
 

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Chances are high from your description and no codes you are dealing with a crank position sensor failure
Lots of similar threads and lots of us have dealt with the same
 

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It sounds as though your truck may have two separate, unrelated problems.

I don't think a failed CKPS would trigger the flashing M & S lights. To properly diagnose that problem a code reader capable of reading the transmission codes is needed. Generic OBDII devices often read engine management codes only. There are something like 14 different faults that can trigger the flashing M & S lights, and without getting the codes read you are shooting in the dark and just throwing parts at it.

That said, in an awfully large percentage of cases it is a voltage problem. The transmission ECU can be very finicky about voltage. You said you replaced the battery and the battery connections are clean and tight, but what about the grounds, especially the transmission ECU ground? Unfortunately it is located under the center console. An easier first step is to unplug and reconnect the connector for the transmission ECU, located under the driver's seat.

Now for the not starting problem. Your description does match the symptoms of a failed CKPS. As redtruck12 wrote, there are lots of threads on that topic. Check the tachometer while trying to start the truck. If the starter is turning over the engine but the tach isn't moving it's likely the CKPS.

Good luck, and please update this thread to share how these things work out for your truck.
 

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Discussion Starter · #7 ·
It sounds as though your truck may have two separate, unrelated problems.

I don't think a failed CKPS would trigger the flashing M & S lights. To properly diagnose that problem a code reader capable of reading the transmission codes is needed. Generic OBDII devices often read engine management codes only. There are something like 14 different faults that can trigger the flashing M & S lights, and without getting the codes read you are shooting in the dark and just throwing parts at it.

That said, in an awfully large percentage of cases it is a voltage problem. The transmission ECU can be very finicky about voltage. You said you replaced the battery and the battery connections are clean and tight, but what about the grounds, especially the transmission ECU ground? Unfortunately it is located under the center console. An easier first step is to unplug and reconnect the connector for the transmission ECU, located under the driver's seat.

Now for the not starting problem. Your description does match the symptoms of a failed CKPS. As redtruck12 wrote, there are lots of threads on that topic. Check the tachometer while trying to start the truck. If the starter is turning over the engine but the tach isn't moving it's likely the CKPS.

Good luck, and please update this thread to share how these things work out for your truck.
Thanks for this awesome detailed response. Sounds bang on. S and M only became a problem a few days in. Will check the ECU harness, and change the CPS (no revs showing when turning over)... After that back to drawing board. Cheers and yeah I'll definitely update once I've got it sorted.
 

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Discussion Starter · #8 ·
Update: Early days, but I replaced the crank sensor yesterday and have not experienced any issues yet - though have only taken her for a couple of spins. Note: Out of all the guides I read about changing the sensor, not one mentioned what a PITA the harness would be... If anyone reads this it is best accessed from above, and you need to push it back towards the firewall to get it out of the bracket first before disconnecting. I would recommend attaching the sensor itself before trying to reconnect harness, and pushing sensor end of plug against the bracket when reconnecting as the cable wants to twist away the whole time (unless there is a way better method I missed in my reading!). Thanks again for all your help, Matt
 

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The CKPS wiring connector is one of the many stupid, frustrating design "features" of the DII I have encountered. And, there is literally NO GOOD reason it needed to be designed that way. The harness side could have been extended down, closer to the sensor itself, or it could have terminated higher up, with the sensor cable made longer. But nooooo, let's make it (almost) as difficult as possible!
 

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Discussion Starter · #10 ·
The CKPS wiring connector is one of the many stupid, frustrating design "features" of the DII I have encountered. And, there is literally NO GOOD reason it needed to be designed that way. The harness side could have been extended down, closer to the sensor itself, or it could have terminated higher up, with the sensor cable made longer. But nooooo, let's make it (almost) as difficult as possible!
Haha yeah I can't count the number of times I redesigned the harness location in my head as I was trying to reconnect the damn thing! By the end I was just glad I hadn't pulled the damn wires out of the plug
 

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So now, on to the flashing M&S lights. What's their status?

BTW, I just noticed the New Zealand flag icon below your user name.
 

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Discussion Starter · #12 ·
So now, on to the flashing M&S lights. What's their status?

BTW, I just noticed the New Zealand flag icon below your user name.
The M&S lights have not come on again. The only thing I can think of is that when I installed the new battery I cleaned the grounds, I used WD40 on them to get them off... (this is just a random guess) but maybe that caused the M&S lights to come on?
 

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Discussion Starter · #13 ·
The M&S lights have not come on again. The only thing I can think of is that when I installed the new battery I cleaned the grounds, I used WD40 on them to get them off... (this is just a random guess) but maybe that caused the M&S lights to come on?
And yeah, live in Chch NZ, a long way from anywhere! But rugged as and lots of mountains and terrain for driving and biking
 
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