TECHNICAL REFERENCE
Released by Snap-on Diagnostics
May 2024
Keith Wray
Snap-on® Diagnostic National Trainer
The most famous partnership in the 4-stroke engine world is the camshaft and the crankshaft. They form a synchronized partnership that produces the most power with the highest efficiency. As synchronized partners, they perform flawlessly. Think about all the moving parts in an engine. The cam/crank, along with the camshaft position sensor (CMP) and the crankshaft position sensor (CKP) partner together to control everything. They control the exact moment the intake valve opens and closes in relationship to the piston position, the ignition timing, the fuel timing and start up. On the other hand, when they are not synced, you can’t say that they don’t “perform” at all: low power, misfire, backfire, no start and a possible come apart can take place, to name a few.
I wrote an article about timing chain elongation a while back, found here. To quote myself from that article, “It is not horseshoes or hand grenades, where getting it close counts. Close is not good enough when setting up valve timing. The marks must line up exactly as shown with the correct cylinder being on top dead center (TDC).”
Obviously, the same would hold true for camshafts as well as the CMP sensor, crankshafts and CKP sensor synchronization, wouldn’t it? After all, they are synonymous with each other. So how do I check for synchronization? As is my standard answer for most all things automotive - it depends on the OEM.
Some diagnostic tools have classes available to learn about cam and crank relationships. Here you can learn about known good values.
Let’s look at another way to determine if they are in sync.
Many OEMs will display a trouble code when there is a problem with cam and crank correlation pointing toward a time chain elongation or belt stretch. Some OEMs offer specific CKP/CMP signal tests. A great example of that is found in the service reset and relearn section on select Snap-on® tools with guided component tests as shown below for a Hyundai®.
It offers a very specific test to determine that the system is synchronized properly. Driving the vehicle after a timing chain of belt replacement could risk damage to internal components if it is not properly synced and calibrated.
The last step is to take advantage of the on-tool guided component test classes. Click guided component tests from the home menu, click on classes and go to power user tests, then power user tests again. Select dual channel, then CKP and CMP relationship.
This presets the scope to everything you need and shows the hook up instructions. This allows you to see the synchronized partnership of the cam/crank.
I don’t know of many things in life where the phrase ‘synchronized partnership’ really fits, but the partnership between the camshaft and the crankshaft is one of them.
Click here for more on this topic, and for so much more, visit Snap-on’s technical article pages.