My check engine light bulb does'nt come on

Connect it to a code reader scan tool. The engine light codes will tell you some of the reason, but Jeff's answer is far better than mine regarding how all this stuff works..

Broken bulb can happen

The turn signal switch and the hazard switch are likly places to look. To checjk the fuses is'nt to take them out and look at them but to test to see if power will go though them, I use a test light ( a tool that looks like an ice pick with a wire coming out of the handle and the handle is clear with a light bulb inside). with the clip connected to a good ground as you touch the back sides of the fuses the light will light if it only lights on one side, the fuse is blown ( does'nt matter what it looks like ) a bad fuse can look good. the turn signal switch is involved as is the Hazard switch. If you pusth the hazard switch and the lights light good then you know that the lights and the sockets are good. You also know that the wires are good . With the key on the turn signals should work front and back ( thier different cicruits) If only working in the front the turn signal switch is bad provided the hazards worked all the way around. Does the high mount stop light work? It works off of it's own circuit on the brake light switch and if no lights work your back to the fuses only after you checked to see if the high mount bulbs are good. Your car is plenty old enough to have them be burnt out. If the high mount doesn't work with the bulbs known to be good and then you check with the test light to see if the power isd getting to the brake light switch. One wire is hot with the key off and another comes hot with the key on ( the cruze control switch in the brake light).

The car runs fine after it warms up? Is it running with the check engine light off? But it does come on with the key before the engine is started? If the coolant temperture senser is bad ( or disconnected someway) the check engine light will be on but the car might run OK at normal operating tempertures. Have the car checked for codes. It's OBDI so you might have to find a service provider that can ceck the codes on this pre OBDII car. If it turly runs good at normal operating tempertures and the transmission is'nt low on fluild then the coolant senser does'nt always turn the check engine light on if it's bad and still reading something but wrong. Truly running good and the coolant is full ( all the way). chage the senser and see what happens as thier cheap and easy to change with commn hand tools.

Hi there,

Your vehicle's OBD computer monitors all your vehicle's electrical emission circuits.

Each time you turn your key, the computer considers this 1 x drive cycle.

When a fault (or out of spec) condition occurs, this will register a fault code in the computer's memory. Some circuits will only trigger the Check Engine Light (CEL) after the same fault occurs a few times. Other circuits will trigger the CEL with just one fault detection.

In the same manner, if the fault condition is only intermittent, the computer may consider the condition recitified, if that fault does not occur after several drive cycles (i.e. the CEL will no longer light up).

The only way to have this resolved is to arrange for your local Mercedes dealership (or authorised service agent) to connect their factory SCAN TOOL.....and read your computer's stored fault codes.

These fault codes will quickly identify the suspected circuits (eliminating unnecessary garage labor costs), allowing quick diagnosis & repair.

Note: Mercedes Scan Tools operate on a different communication protocol. Typical scan tools designed for American & Japanese vehicles use a different protocol, therefore, I recommend this be done only by a Mercedes agent (or European service specialist).

The process of scanning for fault codes only takes 15-25mins (depending on the technician's experience), hence should not cost you much to have this procedure performed.





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I would troubleshoot the wiring and all ground points to eliminate that. Then swap out the ECM to see if is defective.

Does your 'service engine soon' (sometimes a check engine) light stay on if you turn the key to 'run' but don't start it? If this light comes on then the computer is getting power. The no spark could be caused by a bad cam or crank sensor. Since the computer on Dodge vehicles uses both sensors for spark, you can't really tell which one is the issue unless you can connect a scan tool. The scan tool is powered by the port you plug it into, which gets its' power from the cigarette lighter fuse.

First did you reset the computer after replacing the EGR valve if you don't the computer doe'nt reconize the new sensor so it doe'nt reset the peremiters.Then check all passages and lines in the intake manifold there could be a clogg somewhere.Go to www.rockauto.com and you'll find EGR pressure sensor for under $30.00.

common on olds make sure single contact bulbs & dobble contacts are in correct spots
and problem is in the front signals connecters remove bulbs and ull see burnt plastic
replace or clean

turn the key to activate the power but not start the ignition, do this a handfull of times. The check engine light should blink a specific number of times, this can be referenced to identify the problem, after this happens the light should turn off until you have another problem!There's a difference between the "check engine" light and the "engine maintenance required" light (aka "Emission Maintenance Reminder" or EMR light). The EMR light is strickly a reminder that emission system maintenance is due. This includes the EGR valve, PCV valve, & Oxygen sensor. It is program to light at approximately 60,000, 82,500, & 120,000 miles. Because its activated by mileage, it does not necessarily mean that something has malfuction. Unfortunately, the only way to reset it is by using a diagnostic scan tool. Of course, you could always remove the bulb.