CLK Couped

The car: 2002 CLK 320 with 101,000 miles

Car had Check Engine Light AND Check Batter/Alternator lights come on before dying at a traffic light. There was no charge to battery so started with replacement of battery (OEM).

Car then would crank but not start.

Ran code for Check Engine Light thinking it was a sensor. Sure, enough one code came back being Crankshaft Position Sensor.

Took car to a new mechanic who 1.) Replaced the crankshaft position sensor. Then called me saying car still will not start. Needs more time to diagnose.

Mechanic calls back days later stating he found a blown #6 fuse which he says was the result of the harness rubbing on the edge intake until it had worn through the shielding and shorted out. 2.) He replaced (without my permission) the harness and wiring.

A day passes and mechanic calls me again saying he needs to replace the alternator. 3.) So I OK'd the replacement of the alternator.

I picked the car up and find the ABS/BAS brake codes flashing on the screen before leaving the mechanic's garage. He resets the computer and I dry off code-free.

Three days later here I am with the Check Engine Light back on.

Mechanic wants "up to three hours" at $100 per hour to run the code and diagnose. I ran the code at AutoZone came back as P0432.

Not sure where to go from here or really what to believe about what's going on the car. Advice? Suggestions?

Serndipity

By far, the primary cause of an alternator failure is usually the voltage regulator. It's located behind a removable cover, on the rear of the alternator and is an inexpensive replaceable part (e.g. $30). The module is considered a wear item, because it contains the contact brushes. I believe on your CLK320, the module can be changed without even removing the alternator.

The brushes can wear down to a point where they were making enough contact to not have the dash warning light come on, but not good enough to keep the battery charged. When the voltage got low enough in the battery the ignition system shut down and the car will not start, quit dead going 70 mph and leave you stranded.

Note: On cars of this vintage, it's prudent to replace the unit as preventive maintenance.


P0432 indicates that the main catalyst efficiency is below threshold Bank 2.

As the code description implies, the P0432 code means that the vehicle's Engine Control Module (ECM) has detected that the catalytic converter system is not working properly (e.g. is not as efficient as the factory limit settings are expecting).

The ECM monitors the ratio of heated oxygen sensors 1 (front O2 sensor) and heated oxygen sensors 2 (rear O2 sensor). A three way catalyst converter (Manifold) with high oxygen storage capacity will indicate a low switching frequency of heated oxygen sensor 2. As oxygen storage capacity decreases, the heated oxygen sensor 2 switching frequency will increase. When the frequency ratio of heated oxygen sensors 1 and 2 approaches a specified limit value, the three way catalyst malfunction is diagnosed.

Possible causes:

- Catalytic converter deterioration or malfunction
- Exhaust system leaks
- Faulty front or rear O2 sensors
- O2 sensors wiring harness is open or shorted
- O2 sensors poor electrical connection

CLK Couped

Thank you for your reply.

I am inclined to believe the catalytic converter has not deteriorated only because I had it replaced 90K miles ago (or 6.5 years ago). When it went out that time, I heard a very loud sound coming from the car, which I am not getting this time. That is not to say it's not malfunctioning, but two catalytic converters going out on me is a hard pill to swallow.

The fact that this mechanic went in fiddling with the harness and rewiring, as he says "to get the car to start" after changing the crankshaft position sensor gives me pause.

I wonder if it's prudent to start with having the 02 sensors replaced or the 02 sensors wiring looked at first? I am just not sure where to start, short of finding a reliable mechanic.

Serndipity

I'm not a big fan of changing parts without proper diagnosis and troubleshooting. It can be quite expensive.

Also, mechanically, our W208s have been bullet proof and most issues have been in the electricals (e.g. MAF, break light switch, HVAC blower regulator, CPS and as they age, wiring).

CLK Couped

Agreed. I have spent $1K already and that was just for the guy to change out the crankshaft sensor, "fix the harness" and replace the alternator. The money tree (me) is just about bare at this point.

Your reply now has me thinking the alternator probably did not require replacement. Is there a way to check if a new one has been installed?

Thank you again.

Serndipity

If the alternator was replaced, by visual inspection, you should now see a clean, shiny new one. Again, dollars to doughnuts, it's much more likely that only the voltage regulator module needed replacement. Note: When the battery is not being charged, your car will continue to run via the battery, until it's voltage drops to low and you're left stranded.

In your initial post, you mentioned that the mechanic found a blown fuse #6 fuse and replaced or repaired a wiring harness. Note: There are 4 fuse blocks in the W208, each of which likely contains a fuse in the #6 position. A fuse will blow when to much electrical current is drawn, which may be caused by a wiring short circuit or a fault in a down stream device.

It's not really clear, but it's possible that the source of original breakdown may have been a faulty voltage regulator (e.g. worn brushes, shorted diodes).

At this time, except for a CEL due to stored fault code P0432, your CLK320 is running fine. The fault code may have been thrown while your car was experiencing electrical issues. Note: The O2 sensors are heated, which requires electrical power.

My suggestion would be to clear the code and see if it reappears.

MarcusF

It sounds like you're not a DIY type, which is a shame. When new, these were $50K+ vehicles. Age doesn't make maintenance any cheaper. You may benefit from never seeing you current mechanic again and finding either a good Indy or someone who can help you perform maintenance.

This literally discusses fixing a $1000 alternator for $25.

Also, if you put ninety thousand miles on an aftermarket catalytic converter, unless it is a very high quality cat, it very well may be toast as far as your MB ECU is concerned. A CLK is a LEV1 ULEV, so the ECU is paying very close attention to the exhaust. If it's not the cat, it's the secondary O2 sensors. The way to get around this is to lie to the ECU. Using Doorman sparkplug non-foulers to move the secondary O2 sensors further away from the exhaust will cause the CEL to go out. This causes the secondaries to detect fewer pollutants than the primaries. The Doorman fix requires a drill, $10 in parts, and takes less than an hour. Very few shops will perform the Doorman fix.

CLK Couped

Thanks for the replies. I have had the code cleared as a first step. I drove 60 miles highway yesterday and it has not reappeared just yet.

Indeed, I am not the DIY type and need a good mechanic as I am new to my area (Northwestern Suburbs of Chicago) and relied on a family friend's reference that didn't turn out too well.

I will provide an update when warranted.

Thank you both again.

Serndipity

You might find a good MB repair shop here.

http://www.benzworld.org/forums/reco...-repair-shops/