ANGMED

Instrument lights stay on, car does not shift from 2nd gear.

Can someone please say specifically the location in the vehicle to start checking fault PO600 "Serial Comm link malfunction"? Front, back, trunk, etc, etc.

Thanks guys.

MIAMI2000

Same problem with mine..

Maj. Dundee

What do you mean by "instrument lights" stay on? Be specific.

sleepy hollow

I am having the same problem - P0600 code.

I have an 05 CLK320 cabriolet with about 65K miles. Here are the strange behaviors she is showing:

1. Constant messages showing that there are 2 malfunctions: "tail light, left" and "backup light on".

Neither of these is true. I replaced both sets of tail lights and backup lights to no avail. Everything works fine. Messages are clearly erroneous. Contacts are very clean. [I have since learned that "back up" may mean "spare" as opposed to the lights that light when the car is put into reverse.]

2. About every 3rd time the car is started, it starts, but the gauges do not work. The speedometer does not move from zero. The command and menu buttons on the steering wheel have no effect. The "C" and "S" selector button next to the gear shift does nothing and the display next to the odometer does not show anything for the mode (C or S) or the gear selection - P at startup. Also, the fan runs at high speed immediately. This is the definitive clue that we are in twilight zone mode.

The fix is to turn off the ignition, remove the key, and then restart. Usually this works on the first try, but not always.

BTW, the car is drivable, albeit without the gauges and controls mentioned above. Also, no indication of the light bulb issues when in this weird mode.

3. Finally, the check engine light comes on. Usually it resets the next time the car is started. The pattern seems to be (though not sure exactly) that the CE light comes on after the strange mode is reset. Also, the faulty bulb messages disappear temporarily only to return by the end of the journey.

Well, Sunday, I decided to go check the fault codes, but the car was dead. I removed the battery and alternator and took them to the AA store. Both tested bad, so I replaced both (the battery was under warranty and they gave me a new one).

Well, the new battery and alternator did not fix the problem with the messages. The car requires several cycles of starting and restarting to get a fully functioning mode. One thing I have noticed is that there are 2 positions of the ignition switch.

The first position brings up the display, but there are no telltale lights nor is there gauge functionality. The S or C/P are missing from the odometer area.

The second position activates all the telltale lights and brings up the S or C/P. What seems to be happening is that when the car is started sometimes it behaves as though the ignition switch is at the first position, in other words it regresses a step.

Also, I drove it for 2-40 min trips today and managed to get through both with a "no malfunctions" message. However the check engine light was on. So I borrowed a reader from the AA store and found a P0600 message, nothing else. I cleared that code, removed the tester, restarted the car and had everything working with no malfunctions and no CE light. Then I returned the code tester. When I got back to the car, we were back into the soup with the error messages and problems getting a "clean start" .

Thoughts and suggestions welcome.

Cardonman

Had AA scan for codes. Came up w/the dreaded P0600. Truck runs great. At start up early am the CEL came on. Outside temp 20 deg F. Everything still working fine. I restarted the truck after a 10 min drive. CEL off but code still there. Replaced 4x O2, EGR valve, CPSensor this summer. Trucks been great.

Unfortunately battery drained recently and at restart SRS came on. Could this be the issue? Next visit to shop to diagnose SRS. All the fuses are ok under hood and kick panel. Guys/Gals thanks for all the posts that helped point in the right direction.

Cardonman
150, 000 mls and still running strong!!!

MIAMI2000

Could be Key Fob??? i had same issue start up no instrument lights. no gauges working. Fan runnig fast. took key out tapped it started up again running fine. i need new key fob... sounds crazy but that was it... hope this helps

MIAMI2000

Also check Aux batt in front

Maj. Dundee

With your year ML, code P0600 has six possibilities for a CAN problem between the ECM and the respective component (see list).

I'm betting that the code was caused after you installed the MAF sensor. You probably tried to start the truck without remembering to install the connector to the MAF (first possibility in the list).

The SRS code was probably caused by you installing a new battery or charged the battery while the key was still in on position.

In any event, just clear code P0600 and see if it returns. The SRS light can only be cleared with a professional grade scanner.