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Timing belt replacement


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7 replies to this topic

#1 topgun

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Posted August 30, 2010 at 08:20 pm

I am going to replace the timing belt and related parts this weekend on my 03 Neon, had a question. After completing the job, the manual says to use the DRB tool to "relearn cam crank". I assume this is to adjust for any minor changes in the cam position relative to the crank after the new belt install. I don't have access to the factory tool unless taken to a dealer. My question is, does this have to be done or will the computer relearn this on it's own after driving?

I did purchase the complete CRP timing belt kit which also has a new tensioner and water pump. Also have access to a damper remover and installer with the correct 12-1.75 thread. Seems that most I have seen for rent are the wrong thread (12-1.5).

Edited by topgun, August 30, 2010 at 08:22 pm.


#2 topgun

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Posted August 31, 2010 at 03:39 pm

Thanks for the info, it is greatly appreciated. I do have the chrysler puller and installer that comes with the rod (OTC-6075 set). I have read about the tensioner issue but think that may be with the earlier hydraulic models. Will keep an eye out though for the lug on the back. I've got a Actron CP9185 but don't think it has any option to relearn the cam position. Will take a look though.

#3 AllanC

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Posted August 31, 2010 at 08:01 pm

I am going to replace the timing belt and related parts this weekend on my 03 Neon, had a question. After completing the job, the manual says to use the DRB tool to "relearn cam crank". I assume this is to adjust for any minor changes in the cam position relative to the crank after the new belt install. I don't have access to the factory tool unless taken to a dealer. My question is, does this have to be done or will the computer relearn this on it's own after driving


This relearn procedure is not necessary. With the ignition off, there is no electrical function in the crankshaft position sensor and cam position sensor. The engine controller will not know that the crankshaft and/or camshaft have been turned. When the engine is started, signals are generated by both of these sensors and the engine controller relearns the phasing again between the crankshaft and camshaft.

I did purchase the complete CRP timing belt kit which also has a new tensioner and water pump. Also have access to a damper remover and installer with the correct 12-1.75 thread. Seems that most I have seen for rent are the wrong thread (12-1.5).


If you replace the water pump, you will need to remove the rear timing cover. It sits between the engine block and head and the timing belt. To remove this cover you will need to remove the camshaft sprocket.

The service manual indicates to position the crankshaft timing mark such that the #1 cylinder is at top, dead center (TDC) and the camshaft timing mark is aligned with its index. Since this is an interference engine turning the camshaft (with timing belt removed) can cause a valve to open and hit a piston in the TDC position. I modified this procedure and found it to be more forgiving.

After removing the crankshaft pulley assembly and before removing the timing belt, I turned the crankshaft clockwise and stopped it at 90 degrees before top dead center. This also positioned the camshaft at 45 degrees before its alignment to its index mark. I used white marker and indexed / marked 2 sprocket teeth on the crankshaft and camshaft to marks on the engine. These became new alignment marks between crankshaft and camshaft. Then I removed the timing belt.

The reason for stopping the crankshaft at 90 degrees before TDC is that places all 4 pistons at the midpoint of their travel in the cylinder bore. If you accidentally turn the camshaft (it will happen when trying to loosen the camshaft sprocket bolt), no piston is close to a valve and so no inadvertent valve damage will occur.

Note the position and mounting of the tensioner pulley and spring tang to its bracket before you remove them. It will help upon reassembly.

Depending upon the miles on your engine you might want to replace the crankshaft and camshaft seals while you have the timing components disassembled.

#4 Ricketts

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Posted September 16, 2010 at 04:15 pm

Yes, just undo battery cable so system can relearn itself. Replaced mine on my 01 Neon about 1.5 years ago.

#5 GMconvert

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Posted September 30, 2010 at 08:44 pm

Currently changing the timing belt on my '03 Neon. Is there a specific procedure for the tensioner? Do you just turn the allen wrench as far as it will go CCW and tighten the nut? Your help would be greatly appreciated.

#6 AllanC

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Posted October 1, 2010 at 11:50 pm

Currently changing the timing belt on my '03 Neon. Is there a specific procedure for the tensioner? Do you just turn the allen wrench as far as it will go CCW and tighten the nut? Your help would be greatly appreciated.


You insert the wrench into the tensioner and turn counterclockwise. The tensioner setting notch will start to move clockwise. When the setting notch is aligned with the spring tang, tighten the tensioner locking nut. I will send you a PM with a way to get more detailed information.

#7 Rick Anderson

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Posted November 13, 2010 at 11:12 pm

The PCM will throw a code if it spots a change greater than 11° in the cam position relative to the crank. i.e. you skipped a tooth on your timing belt.

The manual says to do the Cam Relearn after changing the timing belt to reset that learned value, i.e. the new normal position between cam and crank.

This value is stored in non-volatile memory, disconnecting the battery will NOT clear it.

BUT, there is NO need to do the relearn. If you install the timing belt correctly, the difference in relative cam/crank position for production tolerances in the belt is so small, its NOT going to make a difference. If you skip a tooth on the belt, its still going to throw the code. I suppose its possible, if you got a belt with higher than normal error in production tolerances and skip a tooth on the belt in the right direction, it might NOT throw a code in the PCM to warn you, but that is unlikely.

Anyone that has gotten the CEL and code for a skipped tooth, right after the install, had installed the belt wrong and had it one tooth off.

Edited by Rick Anderson, November 13, 2010 at 11:15 pm.


#8 ImperialCrown

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Posted November 14, 2010 at 07:20 am

Also any planing/resurfacing of the head will change the cam/crank relationship (ever-so-slightly closer together). That is one reason the the service manual doesn't recommend it. Valve/piston clearance may be the other reason.
The DRB III has a menu item for resetting 'Learned Cam/Crank'. I also don't think that a battery disconnect will reset it. The 'skipped tooth' fault code is P0016.


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