ABS Light...Reverse Boost Hook-Up. W140.

[slimak9]

1992 400SE

I recently had my vehicle boosted by a "well-known" "experienced" (at least I thought) company. Turns out he hooked up the battery terminasl in reverse.

After getting it right, with the vehicle running the ABS light is constantly on. I checked all the fuses and they are fine. I'm guessing it could be a relay???

Where can I find the relay(s) controlling the ABS, or what else can be tested? Or is there a simple reset.

I disconnected the battery in hopes of clearing/re-setting it, but without luck.

Thanks in advance.

[slimak9]

Forgot to mention, that the speedometer also does not work, and in turn the fuel economy guage doesn't read. Everything else on the cluster appears to work fine.

Thanks.

[mbdoc]

Most likely a blown fuse in the "base" module...located in the computer box underhood. Removal of 6 allen bolts required...10A red ATC blade fuse(s)

[wbrian63]

Does the ABS light come on as soon as you switch on the ignition, or after you start to drive the car.

If the speedo doesn't work and you get an ABS light, possibly the problems are related. ABS gets it's base-line readings from speed sensors at the wheels. Interrupt those readings and the light comes on. However, I think the speedo is driven from a sensor on the transmission.

I'd pull codes for the ABS and see what that system reports.

Hope you've got the reverse-leads issue well documented with the dingbat that boosted your car. It is possible that the reverse polarity has fried something and that will cost $$$.

To test the instrument cluster, you should find a small "button" in the center of the knob used to set the clock. Start the car. With the tip of a pen or paperclip, press the button for at least 5 seconds. The odometer display should show ------------- when the cluster goes into test mode. Within 5 seconds, pull out on the clock setting knob and rotate briefly to the right. To move from one mode to the next, pull the knob out again and rotate briefly to the right.

There are 9 testing modes for the cluster
1 - shows gas tank size (odometer will read 1 80 for an 80-litre fuel tank)
2 - momentary fuel consumption in litres per hour
3 - engine oil pressure in bar
4 - engine rpm
5 - engine oil level (0 = level OK, 1 = not OK)
6 - activates oil pressure, economy, tach, speedo, fuel level gauges to 1st quarter of travel - display also reads resistance of outside temp gauge in K ohms
7 - oil pressure, economy, tach, speedo and fuel level move to 2nd quarter of travel
8 - economy, tach, speedo and fuel level move to 3rd quarter of travel. Oil pressure remains at 2nd quarter.
9 - tach, speedo and fuel level move to 4th quarter of travel - oil pressure remains at 2nd quarter, economy remains at 3rd quarter.

This test should allow you to figure out whether the cluster has a problem, or whether the speed sender in the tranny is the culprit.

[slimak9]

I have a analog speedo, therefor I cannot do the above. I believe the digital speedos came in 1995.

I'll check the fuses in the base module this weekend.

Thanks.

[mbdoc]

The cluster may "look" analog but ISN'T... the speedo input is electronic from the ABS control module...base module fuses..

[slimak9]

Sorry, I meant analog display, (odometer, trip meter). I was refering to the test posted by "wbrian63" where I would make the odometer read "------".

I remember removing the cluster to change some bulbs and all was connected electrinically.

I will check the fuses in the "base module" on Sunday as I'm away till then.

Thanks.

[brock_boot134]

Im having the same Speedo/ABS problem on my 83'' 380 SEC Euro. My odometer also went out with the speedo to though. Im interested in this base module. Where can it be found and what am i looking for? I have also been told that the problem might be a faulty ground coming from the cluster, but im not sure exactly which wire the ground is when i look behind the cluster. Also, the only difference other than the odometer would be that my economy gauge does work just fine. Any help would be awsome!!

Brock

[nhodges]

the readout on the ambient temp screen.

[slimak9]

I found 1 of the 3 10A RED fuses in the base module out. Replaced and it works great. Thanks.

The unit on my '92 400SE is on the passenger side, right against the windshield in a box, which its cover is held down by 4 hex screws.