No service engine soon light

[fnawesome]

2000 Jimmy would not pass emissions test because "service engine soon" light will not come on when ignition is turned on. Garage pulled cluster to check for bulbs, said there wasn't any. Said I would need a new cluster. I checked fuses but could not find any bad. Any ideas.

[maxwedge]

No bulbs, there must be some way of illuminating the warning gages, some info here is missing.

[danielsatur]

Take your truck to a local Auto parts store, and Let them connect an AutoScanner to it.
They can can tell, if the Check Engine Light (CEL) is working.

A regular service light has nothing todo with emissions.

[consultIII]

not sure about your cluster but most of the new clusters are all LEDS not bulbs so when parts don't light up its cluster replacement time.

the mil/ses light for your truck is powered by a 10amp gauge fuse #4 in the instrument panel fuse box. so check there first. the ecm grounds the circuit.

the gm factory scan tool can do an illumination check by commanding all the warning lights on

[consultIII]

its a simple one wire circuit powered by the fuse i mentioned to the ipc ses light and grounded by the ecm. ecm supplies grd when required to light led

you could check for power into the cluster at the pink wire A7...is the 12v supply. if you grd A11 and the ses doesn't light the led in the cluster is bad. if it lights....bad ecm??? all very $$ so if I'm wrong don't make me pay.

[danielsatur]

Don't buy a repaird, new cluster, or ECM if needed, there's plenty in the salvage yards.

[fnawesome]

Thanks for the suggestions so far. I have not had a chance to investigate too much further yet. I will start disassembling this weekend. If I do have to replace the cluster do I have to have the odometer programmed. Thanks again.

[consultIII]

oops...pulled up the wrong schematic for your cluster. will get you the correct pin and testing info

[consultIII]

need to know which engine you have 4.3 or 2.2 as pin #'s are different.

[fnawesome]

Originally Posted by consultIII

need to know which engine you have 4.3 or 2.2 as pin #'s are different.

4.3, Auto trans, floor shift

[fnawesome]

Looks like problem solved. Bad LED for service engine soon. I removed the cluster and the back cover exposing the rear of the circuit board. There are removable bulbs on this cluster but they are only for illumination of the gauges. All the warning lights are LEDs soldered to the circuit board. I figured I'd test the LEDs to see if there was any difference between the ones I new were good and the SES. Now I am not an expert in electronics but I did take a course in electronics a few years ago so I have a little knowledge. All the LEDs tested the same except for the SES. There is a resistor across this circuit so I wasn't sure if it was bad. I figured I went this far so I unsoldered the SES LED and the one next to it (which is for "up shift" that is not needed as I have an AT). I used the diode mode on my multimeter and sure enough the ses LED was bad. So I soldered the good LED in the SES spot. Took the board and plugged back into the car and success, the SES came on when I turned on the ignition. Hopefully I'll never have to start a thread here that my SES won't go out.

[danielsatur]

Good job! Maybe you can help Fishingirl, see bad cluster
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