Could the typical water pump/optispark replacement repair disconnect or damage the portion of the harness that connects to the crankshaft position sensor?

I had the usual water pump/optispark replacement on my 96 LT4 a while back and immediately after, began getting the P0336 Crankshaft Position Sensor error code. The shop that did the repair then replaced the sensor, but it still threw the code and told me that because the car still ran fine (which would not have been the case if it was really a bad sensor.), it was a problem with the ECM.

However, the car never threw that code before, so I wasn't sure about chalking it up to coincidence. I did a little research on the internet and found that the P0336 error code can often be caused by that part of the harness being disconnected or damaged.

So, does anyone have an opinion about this? TIA...

 

I believe you check the FSM 6-469 through 6-473 and read, research what's presented to you there regarding diagnostics, clearing and interpreting what you actually experience. There's many situations that can create the DTC. Read and interpret the FSM before the Internet results. Coincidence? Did the shop charge you for the crank sensor replacement after doing it? Did you ask them to or ask for diagnostics? Might matter. How many miles?

I don't own an LT4 but I understand there's maybe some issues with knock modules in the PCM.

A search in the C4 section revealed 23 posts that mention P0336.

 

Thanks for the response. The car has 63k, I've put on about 20k of those and never encountered a P0336 error. The car runs perfectly, it just keeps throwing that code after resets.

I was not charged for a sensor and did not ask for any detailed diagnostics as I've been using the same small shop for over twenty years and from experience, know them to be honest and competent. I just thought it was peculiar that I immediately got that code for the first time after the R&R.

The results I found by first doing a CF search before posting here discuss various conditions that could be causing the code to appear, I was curious as to whether the actual replacing of the water pump and optispark might have been responsible for it in the first place. That, I could not find.

I do have the FSM and was heading there next but was hoping someone might have had the exact same issue under the same circumstances and saved me both having to go through electronic schematics which I seem to be conceptually challenged by and because of some physical limitations, tracking down every diagnostic possibility (I was never supposed to age but I seemed to have wandered into some old guy's body and now can't find my way out).

However, if that is what I have to do then I'll do it. Thanks again

 

I have a 96. I had the optidoc rebuild mine maybe 6 years ago. I had the same code after putting in the rebuilt opti. I did not think I had even touched the crankshaft position sensor during the install. I bought a new one at Autozone and had a small shop put it in for me. It would be hard to do without a lift. Took him 15 minutes to put in the new sensor and everything fine since. Thats all I know as it never made sense to me. Dan

 

I guess it's possible that the new sensor is also bad. If the harness proves to be faulty then that would be the case. FWIW, I asked the tech if the sensor could somehow be bypassed, and he said it couldn't.

 

I have literally no idea why mine went bad during an opti change. The ONLY thought I had, at the time, was shock from repeated knocking on the balancer with a piece of wood and a hammer. Dan

 

It's possible in the process of replacing the water pump and Opti that coolant dripped down onto the connector for the crankshaft position sensor (CKP). The connector on the CKP is female and points upward, acting like a potential catch basin of sorts for anything liquid dripping down from above (like, say, from the water pump replacement). The rubber seal for the CKP can be easily compromised during install, as it's difficult to see and lay hands on/in this area during removal and replacement, which would increase the chances of liquid contaminants getting inside the CKP connector housing and mucking around with the electrical signal the CKP is generating.

My understanding is that the CKP, good or bad, doesn't affect runability, i.e., it sends data to the ECM, but not commands. Someone will correct me if I'm wrong.

You need to make sure the wire pack running down the front of the engine to and from the CKP is routed as far as possible from the high-tension spark plug leads, so as not to potentially pick up outside electrical signals. It's easy during the going-back-together phase of water pump/Opti surgery to route the CKP wires in close contact with one or more of the spark plug leads.

The O-ring that seals the CKP to the front cover is a very tight interference fit. This, combined with how hard it is to visually and physically access the CKP, means it's possible when your guys installed the new CKP they didn't get it (the O-ring) seated fully into the cover - the small bolt and clamp that secure the CKP don't provide enough mechanical leverage by themselves to force the O-ring to seat correctly.

The end result of this would be a potential oil leak, and possibly the CKP sitting slightly cocked to one side after install. Would this make a difference in the sensor end of the CKP being able to "see" properly and thus throw a code? Possibly.

It's all I can do, with my big, fat forearms, to even touch the CKP (and its connector) from above, much less try to remove and replace it in a surgically clean and thorough fashion. And getting my hands in there from underneath is all but impossible, as well - you can see and touch the CKP from under the car but, at least with the meat hooks that pass for my hands, you can't actually get in there to operate.

The solution - and it's easier than it sounds - is to undo the two nuts securing the motor mounts and jack the engine up an inch or so. For me, this made all the difference. Now, you can actually see in there and get your hands in there to do a proper job of replacing the CKP.

Use contact cleaner and compressed air to thoroughly clean the male connector to the CKP (you can do this task from above); you don't want any oily/watery contaminants in there possibly disrupting the electrical signal the CPK is generating. Remove the seal from the connector first, so it doesn't blow off and disappear into some dark nook or cranny never to be seen again.

Before you reinstall the seal, smear (not dollop) a small amount of dielectric grease around the outside of the seal. This will help insure that the seal doesn't deform when you plug the connector back into the CKP. This will also increase the odds of a liquid-tight seal.

Here are a couple of Corvette Forum threads that I found helpful when I replaced my CKP:

https://www.corvetteforum.com/forums...post1567859246

https://www.corvetteforum.com/forums...post1599865302

Please keep your thread updated as you proceed; your experience and (hopeful) resolution will be valuable information to other CF members down the road.

RPO Joe



This is what the rubber (silicone?) seal looked like upon disassembly after the "professionals" at my local Chevy dealer replaced my CKP. A new sensor installed by them didn't resolve my P0336 DTC, so they reinstalled the factory sensor and pretty much left me to resolve the issue on my own. This is what I found when I removed the factory sensor that they had just reinstalled. Dang.



I was able to clean and restore the seal back to its correct configuration, and before reinstalling it I smeared a tiny amount of dielectric grease around the outside of the seal, and then was particularly careful plugging the connector back into the CKP. It slipped in with a smooth, satisfying "click."

 

I hope not to distract from the OP's issues, but I do wish to understand what exactly the crank sensor does in these 96 engines.

The 95 and prior engines don't have them. In addition, the Opti's slotted disk provides hi/lo resolution information to the PCM regarding crank position. Was the crank sensor something that was required by OBD2? Is it something GM added to these cars as a testbed?

IF, as Joe stated, you can run the engine normally without it, never minding the CEL; then what exactly is the point?

 

To confirm what has been said my 96 ran fine with this code when mine went out. Dan

 

That's what I've read from other members, hence my post as to the actual purpose for this sensor in these engines.

A modern engine will not run with a bad crank sensor, or it will run very poorly as the ECM wouldn't know which cylinder to fire.

 

Only a WAG but to provide the 'misfire' DTCs is the CPS required? I've seen mentioned that the P0336 can be removed by a tune so the appropriate place to get a correct answer to the question would be from a very reliable PCM programmer? Does programming it out create any other issues?

 

Don't the 95 and earlier models also have a code for misfire? What sensor do they use to detect that... Opti?

I think this is very relevant to the OP because if this CPS turns out to be a trial run by GM with no consequences whatsoever should the sensor go bad or removed, then tunning it out would be the most logical fix, along with other improvements or changes to the software.

Calling in all tuners.

 

Thank you everyone for your advice and help, I really appreciate it. Checking the route of the wire pack past plug leads would be the physically easiest thing to initially do but the easiest actually being the solution is usually something I only read about, so on to the harness continuity and then the sensor itself after that. I'll definitely update the thread as I work my way through.

Thanks again