Tachometer not working, running rough- Anyone have a Wiring diagram ?

Pierce Vaughn · February 17, 2021

Hello all, hoping to get some help with a 2014 1500 silverado, has a 5.3 engine.

I want to make this short and simple so people will have time to read it and reply- but also want to include everything to give enough info to be helpful, so sorry that this is a little long.

The other day my truck started to run really rough and would randomly die if I came to a stop or if it was idling and my tachometer stopped working.

It seemed to sporadically run sometimes worse and sometimes just rough on the way home from work, and after I parked it when I got home a tried to start it later and it would just turn over and not start at all.

I had a check engine light and had a code for the crankshaft position sensor, so I finally replaced it today and it started up and I think it ran fine for a minute and then I noticed my tachometer wasn’t working again and the code came back... P0335.

So, I disconnected my battery and connected it back and got it to start up and the tach worked and the P0335 wasn’t showing, but the truck ran really bad- rpm dipping and would die immediately or after a short time.

After restarting, the tach stopped working again but it would idle fine this time.

I got it to go back and forth between those two conditions a few times somehow, and ending up with it not wanting to start again.

These are all the CEL codes right now including the new CKP one, and some I think I’ve had for a while!:

P0443

(evap system purge control valve circuit)

P0458

(evap system purge control valve circuit low)

P06DA

(Engine oil pressure control circuit open)

P0335

(Crankshaft position sensor A circuit malfunction)

P0443

(Evaporative emission system purge control valve circuit )

P0458

(Evaporative emission system purge control valve circuit low)

I’m kinda stumped on this one. I known some new ckp sensors need to be relearned, but after replacing it it didn’t really change anything so I’m thinking that wasn’t the problem?

Also, I posted all the codes because I’m wondering if there is any wiring issue that could affect all of those. I think the evap codes I’ve had for a while and it’s hard to fill the gas tank without it clicking so that’s always been like that.

Any help greatly appreciated, and if there is anywhere I can get a wiring diagram of the engine sensor please let me know- the Chiltons manual was no use.

Thanks! -Pierce

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JimCost2014 · February 18, 2021

19 hours ago, Pierce Vaughn said:

crankshaft position sensor

Pretty sure that has to have a relearn process done.

The crankshaft sensor on GMC vehicles is synced to the powertrain control module, or PCM. When the crank sensor is replaced, it must be resynced to the PCM. Without resyncing, the PCM cannot properly determine the position of the crankshaft. The proper procedure for resyncing or relearning the crankshaft position is called the "CKP Variation Learn." The CKP Variation Learn procedure resets the positional information in the PCM's memory and replaces it with updated information from the new crankshaft sensor.

Pierce Vaughn · February 18, 2021

Pretty sure that has to have a relearn process done.

The crankshaft sensor on GMC vehicles is synced to the powertrain control module, or PCM. When the crank sensor is replaced, it must be resynced to the PCM. Without resyncing, the PCM cannot properly determine the position of the crankshaft. The proper procedure for resyncing or relearning the crankshaft position is called the "CKP Variation Learn." The CKP Variation Learn procedure resets the positional information in the PCM's memory and replaces it with updated information from the new crankshaft sensor.

Thanks for the reply,
I was thinking I might need to do that, but I’m still a little confused about why it did the same think with the other CKP-that supposedly was working fine before this problem. I’ve looked up some wiring test and I’m going to try to eliminate the PCM by verifying 5volts one of the wires with the sensor unplugged. The worst thing right now is I can’t get any good wiring diagrams to verify the wiring paths and what reference circuit there is.. I’ll have to find a time when it’s not 10 degrees outside to check some things again! Hopefully later this week.

I’ll definitely get it relearned once I get it working, but it’s going in between not even starting and running bad with a signal rn,

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evad · February 18, 2021

3 minutes ago, Pierce Vaughn said:

Thanks for the reply,
I was thinking I might need to do that, but I’m still a little confused about why it did the same think with the other CKP-that supposedly was working fine before this problem. I’ve looked up some wiring test and I’m going to try to eliminate the PCM by verifying 5volts one of the wires with the sensor unplugged. The worst thing right now is I can’t get any good wiring diagrams to verify the wiring paths and what reference circuit there is.. I’ll have to find a time when it’s not 10 degrees outside to check some things again! Hopefully later this week.

I’ll definitely get it relearned once I get it working, but it’s going in between not even starting and running bad with a signal rn,

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i have only found the gm wiring diagrams on disc but they are BIG $$$$$ lol.i guess we'll have to wait 20 years to get them cheap

Pierce Vaughn · February 20, 2021

So I was doing some testing on the CKP sensor last night. It’s a 3 wire Hall effect, and I have a 5 volt wire (presumably reference/power), then ground, then sensor wire.

I want to verify the wire colors, and see what other sensors use the same power circuit, if anyone has a wiring schematic for this truck (2014 Chevy Silverado, 5.3)
From testing with the multimeter, the 5 volt wire is the light or lime green wire, middle wire is ground(hard to tell color) and sensor wire is purple with dark blue stripe. Do I have this right ?

This CKP is hard to get to and test because it is above the starter... so I was going to do a load voltage test on the reference but haven’t been able to yet.

I did turn the key on and plug the sensor in (with starter out) and still had 5 volts on the line green wire with the old one, the new one dropped 2/10ths of a volt when I plug it in.
I had a 1 1/4 in impact socket that I would touch to the front of the sensor (magnet) and watched the voltage on a multimeter via the back of the plug, and tried it on both wires with both sensors and had no voltage change.
The purple w/ blue line wire has about a little less than a volt, I think like 0.50v-0.70v

I was going to do some further testing in the next couple days, or as soon as I get the chance.

Any thoughts so far on this? I have a handful of more things to check but wanted to see what everyone thought so far.

Thanks- Pierce

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Pierce Vaughn · February 25, 2021

So... good news! I found the issue! I’ll attach some pics if they’ll let me. The bottom wire trunk that goes into the pcm was rubbing on the fender liner and broke through the trunk and the jacket of 3 wires and they were all corroded. The sensor wire for the CKP had just hit the point where resistance won and the wire no longer sent any CKp signal. My oil pressure sensor has been working but I have been getting a code for and open circuit. So all fixed! Only codes I have left are EVAP codes now :/ maybe I’ll look up another thread on that, but now the truck runs!

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