CODE 41: Camshaft Position Sensor (CPS)

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Alibi
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Posts: 3142
Joined: Thu Aug 03, 2006 8:16 am
car:: 89 Lesabre T-type
Location: Pittsburg Kansas 66762
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CODE 41: Camshaft Position Sensor (CPS)

Post by Alibi » Sat Dec 08, 2007 2:26 pm

Introduction

Ah, yes.... our good old friend Code 41. Four flashes, a pause, and one flash per the ECM code reading. O' how do I loathe Thee! Nah, I'm just being melodramatic.

The CPS circuit is made of up three subsystems:


Each of these subsystems can be the cause of tripping the code 41. The most common is the interruptor magnet breaking off the camshaft and falling into the oil pan (a hard hit from a wreck or pothole can cause this). Secondly is the sensor itself failing due to age.

-The sensor itself (~$20 at most parts stores)
-The wiring from the sensor to the ICM
-The Camshaft Interrupter Magnet (~$10)

Circuit Description

During cranking, the ignition module monitors the dual crank sensor sync signal. The sync signal is used to determine the correct cylinder pair to spark first. After the sync signal has been processed by the ignition module it sends a fuel control reference pulse to the ECM. when the ECM recives this pulse it will command all six injector to open for one (priming) shot of fuel in all cylinders. after the priming, the injector are left off for the next six fuel control reference pulses (two crankshaft revolutions) from the ignition module. This allows each cylinder a chance to use the fuel from the (priming) shot. During this waiting period, a cam pulse will have been received by the ECM. Now the ECM begins to operate the injector sequentially, base on true camshaft position. However, if the cam signal is not present at start-up a code 41 will set and the ECM wil start sequential fuel delivery in any old random pattern. A 1in 6 chance that fual delivery is correct. Code 41 is set when the engine is running and the cam sensor signal not received by ECM for last 2 seconds.

Replacement Options

Now read this thread and Padgett's article and you'll see what your options are:

LeSabreT Thread

Padgett's Site

Soo... if you have close to 100k miles on your timing chain and you've established that your cam magnet is indeed missing, then you Really Really Really ought to remove the front cover of the engine and replace the chain, gear, damper, and magnet all at once. You'd be surprised at how much better your motor will run after this. That job is in another article Here.

Just be sure you GLUE in the interrupter magnet to avoid a future code 41 again. JB Weld is the most recommended.

BUT: If you are not in need of a new timing chain, then using the "cheat" method as Excellently outlined in Padgett's article is for you. I personally have replaced the magnet on my car twice using his method.

A few notes on the "Cheat" method:
-Use JB Weld. I've tried both Gorilla Glue and two-part epoxy (I was desperate in both situations) and I personally don't believe either will hold up anywhere nearly as well as JB weld would. My Gorilla Glue'ed magnet came out after 10k miles and my Epoxy'ed magnet has only been in a couple thousand.
-Be sure you have a small mirror... it is Very Very difficult to see what you're doing otherwise.
-To remove the broken bits of a previous Cam magnet, I found that a soldering iron, heated up, works great for melting the plastic magnet housing into enough pieces that they can be easily removed.
-Loosen (but don't remove) the water pump pulley retaining bolts before you remove the belt. This way, you don't have to fight the pulley moving as you try to get enough torque to remove the bolts.

Sources: Alibi's old web page,

Wiki Authors: Alibi

Dates Modified: 1-15-2008, 2-20-2008, 4-20-08

steveX

Re: CODE 41 CAM SENSOR CIRCUIT

Post by steveX » Tue Apr 22, 2008 4:44 am

Material condensed into main wiki article.

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