NewRocketGirl

Yesterday, the C5 had two major stall incidents and one minor hiccup while driving in a 14 mile round trip. One happened while slowed almost to a stop on a very steep hill. I had to let it sit for a few minutes before it would start again. No codes.

The other stall happened while backing into a parking space into a flat parking spot. Stalled, had to wait a few minutes before it would turn over again.

I went into a store for a few, came back out, started it up, and it blew a puff of somewhat smelly exhaust upon starting, which cleared up right away. I pulled out onto the road, and the check engine light came on. I pulled over into the next parking lot, pulled the code, then shut it off:

10 PCM P0335 H - Crankshaft sensor.

When I started it again, the check engine light came back on. I cleared the code with the car running, and the check engine light went off. I drove 7 miles back home, no issues, not even on the steep hill where I had stalled before.

Am I DOA right now? Will it hurt the car to drive it anywhere? Is it just a sensor or is it the crankshaft itself?

I have someone here who can look at the sensor for me. When searching the internet, he found two possible locations for the sensor, left side rear behind the starter or right side front on the timing cover. Which location is correct?

Grounding between engine and electrical system, where is it? I remember seeing something on this forum about it before... maybe the tech notes. I'll look again while waiting for a response.

Otherwise, it is going to be a good hour to 1.5 hour trip to service. Can I drive it to service without causing terrible harm to the car?

junk c5

I had a crank sensor code after my ls6 swap into my 1999 C5. It ran fine under normal conditions but as soon as the power/boost started coming in, it would break up and hesitate horribly. It was throwing a crank sensor code and the sensor was located on the passengers side above the starter.

Pounder

If it does need a new sensor it will have to be relearned with a Tech 2

NewRocketGirl

Thanks! What is a Tech 2? Is that something that a dealer needs to plug into the vehicle or is it something I can do (or buy) myself?

NewRocketGirl

Did the problem stop when you changed the sensor? On the highway, I can be cruising at a steady 70 mph, pretty low RPM's and suddenly I will feel power loss, look down, and the tachometer will be at 0 for about 2 to 3 seconds before the engine starts up again. I suspect it is the same issue as the slow stalls I described in my original post.

Pounder

It is a tool used by the Dealer, some of us have bought clones, around 300.00 ///Dealer pays about 4000.00

NewRocketGirl

Going back to my first post, I currently have the Vette parked in the driveway, afraid to take it anywhere. The nearest dealer is about an hour away, and I won't take it to anyone local. I am trying to decide if I should try to drive it to the dealer, or arrange a tow.

Other than stalling, is there any thing else bad that I can do to the vehicle by trying to drive it to the dealer with this failing sensor and the check engine light coming on?

lionelhutz

I've read lots of cases of people not having to relearn the replacement. You could take your chances, but if it doesn't work you'd might need a tow to take it somewhere.

Cherokee Nation

My 08 with a small cam,LTs and Dyno tuned has been doing the same ,but only at a low speed take off. It will stall and I put it back into park then restart. It has been doing this for a couple of years. My code reader shows no codes. One shop told me it was in the tune??

Cherokee Nation

Sorry wrong Forum.

foggy

No Relearn necessary..
Just replace the the sensor and you're good to go !!

Pounder

Pounder

The CKP sensor, and its reluctor wheel are the cornerstone of the engine management system used in Gen III and Gen IV GM vehicles. In the Gen III engines, and the early Gen IV engines, at the end of the crankshaft, there is a “24x” (24 tooth) reluctor wheel. Around 2006, GM switched a “58x” (58 tooth) reluctor wheel in the Gen IV engines. As the crankshaft rotates, the CKP sensor, which is installed in the engine’s front cover, detects when a tooth on the reluctor wheel passes the sensor. This signal is sent to the PCM, and the PCM uses it to reference when to fire the ignition system and activate the fuel injectors. The PCM also uses this signal input to detect when unexpected changes in crankshaft rotational speed are detected, which is generally indicative of a “misfire”.

The factory service manual explains that slight manufacturing variances in the crankshaft, reluctor wheel, and/or CKP sensor can make misfire detection very difficult. Thus, the CKP System Variation Learn Procedure exists to teach the PCM how these components are unique to the engine.

lionelhutz

On the service DVD 2001+ says to do the relearn and 2000- doesn't. I can't even find the procedure in the 2000- years.

The CKP sensor is behind the starter, not at the front of the engine.

Pounder

this was just a article I found online, I would do the relearn if the car was mine !!!! the detonation if the sensor is not relearned is the premise !!!

lionelhutz

The camshaft or CMP sensor is in the front cover, not the crank or CKP sensor.

I'm curious if the 2000- cars can be relearned or not. The DVD service manual doesn't have any info on doing it on these earlier cars.

At any rate, you can replace the sensor and it will still drive OK. DTC P1336 or P0300 might set.

foggy

I have a 2000. I was out in the boonies when mine bit the dust..
Found an independent shop to replace it... I was with him the entire time..
We did NOT do a relearn and have been fine for the last 3 years..

Maybe different years do require a relearn.. Just giving my experience

Pounder

the relearn is so the crankshaft sensor and PCM are on the same page to prevent detonation so slight the knock sensors and you can't tell, next thing you know you have piston damage, namely broken ring lands !!! Pay me now or pay me later so the saying goes !!!!! Your car so ------ ( especially with a manual trans)

lionelhutz

But is the manual right and it doesn't exist on a 2000 or is the manual wrong and it does exist on a 2000?

Pounder

I will give you the info again, do as you wish !!!
Crankshaft Position Sensor Learn Issues on Gen III and Gen IV Engines
Vince Geglia
Trifecta Performance, Inc. (www.trifectaperformance.com)
04/09/2007

Disclaimer: The authors have taken every measure possible to ensure the accuracy of the information presented here, but cannot be held responsible for any inaccurate information presented. In other words, proceed at your own risk.

Introduction

With regards to powertrain control module (PCM) custom programming, have you ever seen people discuss the dreaded “crank relearn” issue? Usually this issue is associated with frustration at having to pay the GM dealership upwards of $100 to do something to your ride so the Service Engine Soon instrument cluster light (a.k.a. SES light) stays off. And perhaps some of that performance you lost is restored. This article discusses what “crank relearn” is, why it’s a problem for custom PCM programmers, and what the dealership is doing to your vehicle to fix it.

What is “crank relearn”?

“Crank relearn” refers to a GM service procedure that has to do with the calibration of the PCM to a specific engine’s crankshaft position sensor (CKP sensor). When your Gen III (LS1, etc) or Gen IV (LS2, etc) based car or truck was put together and factory-tested, one of the procedures it went through was the “crank learn” procedure. The PCM has the ability to contain detailed information about how the specific engine in your car operates, and it must have this information in order to run the engine optimally under all conditions. One key piece of information pertains to how the CKP sensor reports its signal to the PCM.

If a vehicle’s PCM is changed out, there is a chance the new PCM will contain incorrect information about how the CKP sensor reports its signal to the PCM. If the new PCM’s information is incorrect, and the PCM cannot self-correct it, it will set the P1336 Diagnostic Trouble Code and turn the SES light on. Aside from the annoying SES light, vehicle performance may be affected, and emissions systems may be compromised.

Introducing the Dreaded P1336 Diagnostic Trouble Code (DTC)

According to the GM factory service manual, the OBD-II trouble code, P1336, is defined as follows: DTC P1336 CKP System Variation Not Learned. The factory service manual does not enumerate all of the symptoms of this trouble code, but after consulting a professional custom PCM tuner, it was learned that aside from the annoying light on the instrument cluster, the other symptoms exhibited may include: poor vehicle performance, and loss of misfire detection diagnostics.

This DTC is particularly nasty, because simply clearing it by disconnecting the battery, or clearing it using an OBD-II scan tool will not address the problem. The code will be set again later unless the vehicle is run through the actual “crank relearn” procedure.

Fixing the Dreaded P1336 DTC

There is only one way to properly fix the P1336 DTC, and that’s to perform a “crank relearn” procedure, or as the GM factory service manual procedure calls it, the CKP System Variation Learn Procedure. This procedure can be initiated and performed by GM’s be-all end-all scan tool, the Tech-2. It can also be performed by some aftermarket scan tools. Furthermore, some of the PCM tuning software applications are capable of initiating a “crank relearn” procedure.

For most enthusiasts that encounter this issue, the best course of action is to bring the vehicle to a local GM dealership and have them perform the procedure. Unfortunately most dealerships will charge a modest fee for doing this (upwards of USD $100 in some cases).

How to Avoid the Issue

Unfortunately, the only sure-fire way to avoid possibly running into the P1336 DTC is to keep the engine and PCM original. Seeing as this is unrealistic given today’s performance-minded enthusiast, there are several ways to reduce the risk of running into the issue:

When ordering custom programming, use your original PCM. Don’t opt for “PCM swap” services! Either find a custom mail order PCM tuner that can use alternative programming methods (e.g. hand-held devices) or deal with the down-time and send your PCM in. Insist on keeping your original. In 99% of the cases, this will prevent the DTC P1336 from appearing.

Understand that major changes that dramatically affect how the engine runs may cause P1336, even if you retain the factory PCM. Camshaft changes or other internal modifications can cause the DTC P1336 to appear.

Using a PCM from a vehicle that had a different engine type dramatically increases the chances of encountering this issue. Starting in 1999, GM used the same PCM on virtually all of their V8 engines, from the Vortec 4800, to the LS1, to the Vortec 8100. Using a PCM from, say a Vortec 4800 in an LS1 vehicle, even after it has been reprogrammed for the LS1 has a much higher chance of running into this issue then using a PCM from another LS1 vehicle in an LS1 vehicle. This is a major issue for many mail-order PCM tuners because they buy PCMs in quantity from wrecking yards and don’t keep track of which type of engine family they came from.

Technical Details

This section delves into the technical details surrounding the CKP system, and discusses the actual CKP System Variation Learn Procedure, as documented by GM’s factory service manual.

How the CKP System Works

The CKP sensor, and its reluctor wheel are the cornerstone of the engine management system used in Gen III and Gen IV GM vehicles. In the Gen III engines, and the early Gen IV engines, at the end of the crankshaft, there is a “24x” (24 tooth) reluctor wheel. Around 2006, GM switched a “58x” (58 tooth) reluctor wheel in the Gen IV engines. As the crankshaft rotates, the CKP sensor, which is installed in the engine’s front cover, detects when a tooth on the reluctor wheel passes the sensor. This signal is sent to the PCM, and the PCM uses it to reference when to fire the ignition system and activate the fuel injectors. The PCM also uses this signal input to detect when unexpected changes in crankshaft rotational speed are detected, which is generally indicative of a “misfire”.

The factory service manual explains that slight manufacturing variances in the crankshaft, reluctor wheel, and/or CKP sensor can make misfire detection very difficult. Thus, the CKP System Variation Learn Procedure exists to teach the PCM how these components are unique to the engine.

Partial Text: DTC P1336 CKP System Variation Not Learned from GM Factory Service Manual

The following text is quoted from the 1999 GM F-Body Factory Service Manual:

“
Circuit Description

The Crankshaft Position (CKP) sensor sends pulses to the PCM as the reluctor wheel teeth rotate past the CKP sensor. The PCM uses the CKP pulses to synchronize the ignition and fuel injector operation, and to time the interval between each CKP pulse. The PCM determines when an excessive change in crankshaft speed occurs by comparing each new time interval with the previous interval. A misfire causes an unexpected change in the crankshaft speed. A certain amount of acceleration/deceleration is expected between each firing stroke, but if the crankshaft speed changes more then an expected amount, the PCM interprets this as a misfire. The interval between the CKP sensor pulses is extremely small. At high engine speeds, slight variations in the following components make misfire detection difficult: Crankshaft, Reluctor wheel, CKP sensor. The PCM learns variations during the Crankshaft Position System Variation Learning Procedure. The PCM compensates for these variations when performing detect misfire calculations. Only a scan tool can command the PCM to perform the Crankshaft Position Variation Learning Procedure again.

Perform the learning procedure after the following actions: A PCM replacement, Any operation or repair involving the crankshaft, the CKP sensor, or the CKP to reluctor wheel gap relationship, An engine replacement, The ignition switch is in the ON position until the battery is drained.