A Hyundai and a P0335

It didn’t take long to catch the no start condition and see the cause. The CKP sensor flat lined at 5.0 volts instead of being pulled high/low as it should have been.

This 2004 Hyundai Santa Fe was towed in with a complaint of an intermittent no start. With 78,000 miles on the clock, it would also provide an opportunity to not only practice my diagnostic skills, but my customer service skills as well. After all, with that kind of mileage, there had to be other areas of needed maintenance I could recommend.

If you’ve read my work for any length of time, you know how I feel about doing a thorough inspection on every car I service. It is a professional and moral obligation to provide my customers with the benefit of my experience and training, and to help them keep their cars safe and dependable.

The 2.4 four cylinder cranked right up for me in the lot, and I drove it into the bay. The Malfunction Indicator Light (MIL) was on; perhaps that would provide the clues I needed to quickly diagnose this problem. I retrieved a code P0335 from the Engine Control Module (ECM) — a Crankshaft Position Sensor (CKP) circuit malfunction. That would do it. According to the Hyundai service site, this code sets when the ECM does not see the CKP pulse signal during a four-second period while cranking. With no CKP signal, the engine would not start.

With the upper timing belt cover removed, it was easy to see the belt was overdue for replacement. The sensor failure may have been a stroke of luck. Imagine the problems she would have had if this belt failed on the interstate!

Tracking the Problem
Now the question is whether the sensor itself had a problem, or if the fault was in the wiring. I connected my scope to both the CKP and Camshaft Position Sensor (CMP) signal wires and repeatedly started the car. It didn’t take long to see the signal from the CKP stuck high at 5.0 volts, resulting in the no start the customer complained of.

I checked Identifix for similar problems and found the majority of the cases reported listed a failed sensor as the root cause. I had no reason to doubt at this point that the same thing would cause my failure. I had a full 5.0 volts from the sensor and the ground trace looked fine, so I was confident that the problem wasn’t related to a power/ground issue in the circuit.

I looked up the flat rate time for replacement of the sensor. The time allowance was 3.1 hours and told me right off this was not going to be a quick fix. The sensor is located behind the timing belt cover, with the harness routed behind the timing belt, passing through the cover behind the power steering pump mounting bracket and then passing over the valve cover before connecting to the harness at the other end of the engine. More than likely I was going to have to move the timing belt, so I’d better take a look at the belt condition before I put together my parts list.

With the crank sensor out in the open, I knew the timing belt would have to come off in order to route the new one. That explains why the flat rate time listed is a tad more than the time allowed for timing belt alone.

Make a List, Check it Twice
As I mentioned, the Hyundai had more than 78,000 miles on it, and according to my aftermarket service source, the timing belt was recommended at 60,000. But I’m sure you’ve seen the same thing I’ve seen: Most customers don’t like spending money on preventative maintenance, especially on jobs like timing belt replacements where the cost can easily exceed a few hundred dollars.

I suspected I’d see the OE belt still on this engine, and I wasn’t disappointed. The belt had obvious stretch in it as evidenced by the slop in the belt between the two cam sprockets. Also obvious were the splits running across the top of the belt. The belt was way overdue for replacement, and now would be a good time to do it.

While accessing the belt top cover, I took a look at the accessory belts and found them just as worn. Because all the belts would have to be removed during the sensor replacement, the only cost to the customer would be the additional parts needed. The engine does use a balancer shaft, but replacing it would add very little additional time to the job. Because the water pump is mounted under the timing belt cover, it wouldn’t be a bad idea to change it out as a preventative measure, and I recommended a new hydraulic timing belt tensioner to be on the safe side.

The old CKP was cracked right at the wiring pins. Think that was the problem?

Ready, Set, Go
With parts in hand, it was time to go at it. The 2.4 is a double overhead cam design, driven by one belt. A balancer shaft is also used to keep things smooth. The first step was to review the service procedure and then it was time to go to work.

From the top, remove the engine cover, then the coil cover and engine cover brackets. The CKP sensor harness runs under the coil cover, then under the injector cover at the rear of the engine. Removing this cover requires the throttle cable bracket to be removed, but you can leave the cables attached. You only need a tad more clearance to remove the injector cover. While you’re upstairs, remove the upper timing belt cover and set it aside.

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The crank pulley and water pump pulley are both positively located to their mates. Here you can see the small dowel that locates the crank pulley to the gear.

Raise the car and remove the accessory belts, water pump drive pulley and crankshaft pulley. Look close at the crank pulley. You only have to remove the four bolts that hold the pulley to the crank gear — leave the center bolt alone. Notice that the crank pulley is located to the crank gear with a small dowel pin. Be sure to line it up properly when putting everything back together.

The water pump drive pulley is best removed by loosening the four bolts while the belt is still on and tight. It’s a tight fit, but can be done. Removing the pulley, however, may require raising the engine a tad off of its mount for clearance. Notice that the water pump pulley also is positively located by a small notch on the pulley itself. Don’t force this back on wrong.

Now remove the lower timing belt cover. With the timing cover removed, it was easy to see that the timing belt would have to be removed in order to route the wiring for the replacement sensor.

Align the timing marks with the No. 1 cylinder at top dead center of its compression stroke. In my case, there was enough slack in the old belt to allow it to jump timing one tooth. I like to use White Out, borrowed from our receptionist, to mark the engine and gears for reassembly. Now carefully remove the tensioner assembly and the belt. One additional step would be required for sensor replacement. The harness runs behind the power steering mount, so the four bolts that keep the bracket in place would have to be removed and the assembly positioned off to one side.

One last check to make sure it’s fixed and to add to my database. Red is system power to the sensor, green is system ground and blue is the pulse signal the ECM wants to see.

Wrapping Up
The new sensor was installed, and its harness routed. A few notes on reassembly. While I was able to align the two cam sprockets without one, a cam holding tool would have made life easier. Once all the timing marks are aligned, install the tensioner and rotate the crank at least two full turns to verify that the timing marks are correct. When you’re confident that all is as it should be, assembly is pretty straightforward.

Now it’s time to verify the repair. I connected my scope to the new sensor and started the engine. With one channel monitoring power in, one monitoring ground out and one dedicated to the signal itself, I was able to test it all at one time. With the repair verified, and the timing belt known to have been installed correctly, this was a good time to get a reference pattern I might be able to use later.

This “known good” relationship between the CKP and CMP sensors could come in handy on other Hyundai 2.4s. Timing belt wear or out of time issues can be easily spotted by comparing this pattern to the one in question.

The last capture is one of the CKP and CMP together. Had I checked this earlier, I would have seen the “tooth off” timing belt by comparing the synchronization of these two signals.

Crank sensor failures are not uncommon, and usually are simple repairs. But this customer was lucky. Her repair allowed her to also address much needed maintenance work before it left her stranded, and at a minimal additional cost.