blotty

Hello,

I'm having a problem starting my CLK350. I replaced the battery about 3 weeks ago. The issue went away for about 2 weeks and then reappeared. It seems worse when temperatures are below 40deg F.

I left the car sitting over the past weekend and measured the battery with both terminals connected prior to starting and got 4VDC.

I jumped the car and it strated right up.

With the car at idle, the voltage is only 10VDC, but as I raise the RPM's to ~1500, the voltage goes to 14.3VDC, leading me to believe the alternator is good and there is an imtermittant drain when it's cold.

On days the drain doesn't appear, the voltage at idle is 12.3, which I believe is normal.

When the issue is present, the car won't start immediately after turning the ignition off.

I pulled fuses 1,2,8,9,21,22,25,36,41,47, and 64 and left if overnight, but the drain still occured.

Yesterday while driving home, the passenger side low beam started blinking and the speedometer stopped working. I'm guessing that was caused by the fuses being removed. I also have an ESP and ABS light.

The tire monitor system is currently inop because the sensor was damaged when I recently had new tires put on, so they just installed a regular valve stem and oredered a replacement. Not sure if this could have anything to do with it.

Around the same time I started intermittantly getting a P0128 CEL for the coolant temp.

Any ideas how to troubleshoot this would be greatly appreciated.

Glyn M Ruck

P0128 means the engine is running too cold. Replace your electronic thermostat. However low voltage can cause spurious codes etc so sort out first.

If the alternator is cutting out at approx 14.2 volts it is operating correctly.

New batteries can fail. Have it properly load tested.

The cause of parasitic battery drain is usually something on the CANBus not going to sleep. The most common culprits are the front seat modules (although rare by 2008) and the HVAC sniffer fan in the overhead console.

Unplug both & see if the drain continues. If it does you are going to have to take a multimeter to the front & rear fuse boxes. Close down the car & shut the doors. Wait for the CANBus to sleep. Approx 20 minutes. Then remove fuses in the front & rear SAM's one by one & read which circuit is drawing power.

Good luck!

blotty

Thanks Glyn!

I tried disconnecting the seats and sniffer fan as well as replacing the battery, but no luck. It actually got worse.

I jumped the car today and had 5 codes. P0562 (2times), P0121, P2158, and P0128. I also has the ABS, SRS and ECP illuminated.

Prior to jumping the car, the engine fan turned on and was really agressive. I noticed this the past few days as well. I also noticed that the shifter light (P) and wrench in the center console was illuminated.

I heard clicking coming from the relay (B) on the fuse panel in the trunk and also clicking and a faint squeal coming fromthe Mass Air Sensor.

The headlights were blinking and they were turned off.

So, you think thats all strange? Here's where it really went crazy... Once I jumped the car, I let it run for a bit and then turned it off and removed the key, only the car didn't turn off!!! It kept running with no key in the ignition!!! I could put it in gear, but it wouldn't move. I had to disconnect the battery to get it to turn off. The ignition now seems to be locked as well.

Any ideas??? Thanks, Jay

Glyn M Ruck

You need to get this car onto a Star. The codes are spurious & likely caused by low voltage.

Something is obviously haywire. Could be the EIS which is top of the control pyramid, a failing or corrupted SAM, a CANBus short etc.

I'm suspicious of the EIS but with so many issues that is purely speculative. Endless jump starting can damage a SAM.

P0562 System Voltage Low
P0121 Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance Problem
P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
P2158 Vehicle speed sensor B

Good luck!

blotty

Thank you Glyn. I agree, I need to get this on the star, but due to location, it's not really an option for me right now as I live on an island.

I did remove the front SAM after the last message. I noticed that the heating and AC controls on the dash remained lit, so I pulled fuse 41 on the interior SAM. With those two out, the drain is gone. Prior to pulling those two, I disconnected and reconnected the radiator fan (was turning on aggressively at start prior) and now it doesn't turn on when vehicle is started.

It's been a few days with the SAM and fuse 41 out and no drain whatsoever, so I'd say you were right on, between the EIS, SAM and CAN-Bus.

I plugged the 12VDC back into the SAM 24 hrs ago and still no drain.

Correct me if I'm wrong, but if it is the EIS, I would be getting active readings at the SAM with the key out and doors shut? All I have is a multimeter at the time, but do have access to an O-Scope if necessary.

CAN H active: 0.65V, dormant: 0.025V

CAN L active: 4.65V, dormant: 11.0V

Do you happen to have a link to the wiring diagram for a W209 CAN-Bus?

By the way, I thing the SRS was my fault as I disconnected everything under the seat, when trying to eliminate the heated seats from the equation. When I realized, I connected it back up, but believe I need it hooked up to clear it. My scanner won't do it.

Thanks in advance for all the help.

Glyn M Ruck

Radiator fan should only start at cold start if the HVAC is on. You have the HVAC defeated so that makes sense.

Yes the SAM is still active at dormant draw with key out & CANBus sleeping. Opening the drivers door wakes up the CANBus.

I don't have a wiring diagram for W209 CANBus's. All I have is in the Wiki.