Reading Diagnostic Trouble Codes

When the check engine light comes on and stays on (after start-up), this indicates that a code (or codes) has been stored in memory. To retrieve this information for purpose of troubleshooting, cycle the ignition switch ON-OFF-ON-OFF-ON within five seconds. The check engine lamp will then flash the DTC(s). Each code, if there is more than one, will be preceded by a 4 second pause, to distinguish it from the previous code. An example of a DTC would be as follows:

* Lamp on for 2 seconds, then turns off.
* Lamp flashes 4 times, then pauses, then flashes 1 more time.
* Lamp pauses 4 seconds, then flashes 4 times.
* Lamp flashes 7 times.

The two DTC's displayed, following the two second pause, were 41 and 47. Whenever the malfunction indicator is operated, as many DTC's as are in memory will be displayed. At the end of the sequence, it will flash 55, which indicates it is the end of the stored codes.

Mopar1973Man Note: Its still suggested to used a code reader. These errors are very general in description. A normal code reader will show more information. Like error code 43 Ignition coil circuit could be a misfire code (P0300 to P0310) when a error code reader is used you can see the cylinder number.

Clearing Diagnostic Trouble Codes

When the problem has been sorted out and repaired, you will have to erase the DTC(s) from memory to shut off the CHECK ENGINE light. The proper way to erase is with the DRBII scan tool, or equivalent. If you do not have access to this tool you will have to take the vehicle to a shop that does. If the cause for the blown trouble code is indeed repaired, the memory will automatically be cleared by the engine controller after 50 start-ups.

Mopar1973Man Note: Better explanation at this link.

The first thing you need to do is pull the valve covers off the engine. You'll need a socket and a 3/8" ratchet. Loosen all the bolts till you can lift the bolt up. Don't bother removing the bolts from the valve cover. Once you got that the valve covers will come off. Just lift the 6 covers straight up.

Now you need to use your 1/2" ratchet and the 15/16" socket to rotate the alternator. You want to turn it towards the passenger side (or towards coolant bottle). You want to get the gear to be in the TDC (Top Dead Center) using the timing pin found under the injection pump.

Mopar's Notes

Once TDC found using the timing pin mark the damper and the gear case in one spot denoting TDC. There is a reason for this...

Now check the rocker arms on number 1 cylinder. both should be loose at this point. If not check both rockers on cylinder number 6. If cylinder number 6 is loose then your 360° out on the crank, so rotate another 360° till you line up on your TDC marks again.

WARNING! Be sure that the timing pin is pulled out of the gear before rotating the engine. Otherwise damage to the timing pin will occur!

Here is the valve clearance measurement

But if you followed my suggestion above now you wouldn't need to mess with that pin anymore! But for making things simple we'll start at TDC of number 1 cylinder with both rockers loose.

now rotate the engine crank 360° again so now cylinder number 6 rockers should be loose. Using your new timing marks on the damper.

Now reassemble the valve covers.

I set my valves today, figured I would show everyone how I do it. As long as you know the firing order and valve lash (which are both on the cummins id tag) you can set the valves.

This is called the valve overlap method. Basically the pistons have running mates. Running mates are pistons that go up and down together in exactly the same positions, as in they both hit TDC at the same time. The difference is that one of them is on the compression or power stroke, and the other is on the intake or exhaust stroke.

To find the running mate, you simply take the firing order and split it in half. Our cummins' firing order is 153624. So splitting it in half would mean 153-624. If you put the second number under the first, you would have 1/6 5/2 3/4 So 1 is 6's running mate and 5 is 2's, 3 is 4's.

Since the running mates are 360 degrees out of phase, when one of the hits TDC compression/power stroke, the other is hitting TDC exhaust/intake stroke. This is perfect for setting valves because you can simply watch the running mate of one piston and it will be on the exhaust stroke with the exhaust valve open, when it hits TDC and transitions to the intake stroke, the intake valve will open. Once you see that intake valve move, stop. This is TDC, or as close to TDC as we need to be. The running mate will be on the very end of the compression stroke and the start of the power stroke and the valves will be on the opposite side of the cam lobe since they must be shut during the compression and power strokes. You can now adjust the running mates valves, intake and exhaust.

For example. To do the valves on #1, you would watch #6. The #6 will open and close the exhaust valve and once the exhaust valve closes and the intake starts to open, you stop and now you know it is at TDC. Since 1 is it's running mate, you know 1 is on TDC compression/power so you can do both valves on #1.

Now look down the line and you will see that the exhaust valve on #2 will be open. Since 5 is after 1 in the firing order, 5 will be the next valves you adjust, and since you watch 2 because it is 5's running mate, you will watch #2's exhaust valve close and start to open the intake, you stop and do the valve on number 5.

Basically you will be turning the engine 120* to do each valve. You will do them in the same order as the firing order.

Here is the reference order. Do 1 by watching the valves on 6. Then 5 by watching 2. Then 3 by watching 4. Then 6 by watching 1. Then 2 by watching 5. Then 4 by watching 3.

The next one you watch will have the exhaust valve open so that will be a clue that you are doing it in the right order. It is a very fast and bulletproof way of doing it. It works on any engine also. Just split the firing order and stack them and you have your running mates like I showed earlier, it always works.