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02 Envoy keeps blowing ETC #23 fuse
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scott121569
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Feb 16, 2013, 11:08 AM
Post #1 of 10
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02 Envoy keeps blowing ETC #23 fuse
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02 GMC Envoy 4x4, Reduced engine power light came on, I put a new throttle body and ignition switch on, still kept blowing the ETC 23 fuse, Before I buy a new PCM, I checked the PCM C1, C2 & C3, I have narrowed it down to when the PCM C2 is pluged in it blows this fuse, but if I only have the C1 and C3 pluged in it doesnt blow. So that means it isnt my PCM (right), but how do I find out what is the connection between the C2 and blowing the E T C 23 fuse. I have been working on this for 3 weeks now and no one can come up with a solution... any suggestions or help is greatly appreciated.
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Discretesignals
Ultimate Carjunky
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Feb 16, 2013, 12:06 PM
Post #2 of 10
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Re: 02 Envoy keeps blowing ETC #23 fuse
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I see the problem your having trying to diagnose this. The ETC fuse protects a power feed that goes to the PCM itself. They integrated the ETC module into the PCM.
The problem is you can't trace the circuit once it goes into the PCM. There is no service information that I can find to give you a hint as to what the fuse actually protects.
I can only assume that it has something to do with ETC system since the fuse is labeled ETC. Without seeing the electrical schematic of the inside of the PCM, it is near impossible to see what that this circuit actually powers. GM doesn't supply PCM internal schematics in any of their service information. (which is BS) that I can seem to find. If the dealer had this vehicle, they would probably call up an engineer.
Don't know why plugging in C2 causes the fuse to blow. Since most of your engine sensors are on C2 could only assume the ETC circuitry inside the PCM is activated once the PCM is powered up and C2 is plugged in.
My suggestion before checking every single circuit coming out of the PCM for shorts is to check circuits of the the components on the ETC system.
Such as: ohm checking the ETC throttle motor control wires for shorts to ground or each other. Checking APP and TPS sensor voltage supply circuits for shorts to ground.
If all that checks good, you have no other choice but to check every single circuit coming out of the PCM for shorts to ground (besides ground circuits). This also means powering up output devices and measuring for excessive current draw. Once you have eliminated all possible shorted circuits, the only thing that is left is the PCM itself.
If I run into any other info on what actually this ETC power circuit feeds, i'll update.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Feb 16, 2013, 12:27 PM)
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speed
User
Feb 16, 2013, 12:19 PM
Post #3 of 10
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Re: 02 Envoy keeps blowing ETC #23 fuse
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Have you traced the exact wire to the pcm and checked for shorts? according to SI that circuit goes from the fuse to connector 3 not connector 2 at the pcm.
GM ASEP 26 SCC Milford ASE certified in Brakes and Electrical on Thursday April 5th 2012
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Discretesignals
Ultimate Carjunky
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Feb 16, 2013, 12:32 PM
Post #4 of 10
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Re: 02 Envoy keeps blowing ETC #23 fuse
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Think about it. If the pink wire from the fuse to the PCM had a short to ground, the fuse would blow with connector C3 unplugged.
Look at your SI information and try to figure out what the ETC fuse protects. I am using Alldata, so SI may have more info.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Feb 16, 2013, 12:34 PM)
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scott121569
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Feb 16, 2013, 12:32 PM
Post #5 of 10
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Re: 02 Envoy keeps blowing ETC #23 fuse
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I unplugged the C3 which has the pink wire which is the ETC wire that goes to the fuse box, it didnt blow the ETC fuse, Once I figured out the it wasnt the ETC wire from the fuse box to the computer, I unplugged the C1 & C2 to stop anything from drawing off the computer, the fuse didnt blow. so now I have the C1 & C3 plugged in still didnt blow the fuse, as soon as I plugged in the C2, it blew fuse 23. I have checked everything individually.
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Sidom
Veteran
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Feb 16, 2013, 12:45 PM
Post #6 of 10
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Re: 02 Envoy keeps blowing ETC #23 fuse
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When dealing with shorts, it helps to know when there is a short & when there isn't.......They make short indictors that you can hook into the fuse holder or if you have a test light you can use that.....You hook the clip to batt + and then probe the load side connector of the fuse holder, if the light lights up, then there is a short in that circuit.... It helps to see all the loads on that circuit and you can individually disconnect those, if the light stays on then the short is in the wiring... At this point you can start wiggling harnesses to see if you can get the light to go out or even flicker......If it flickers you are in the right spot.....
One quick short cut you can take that may save you some time.......Since this is a 4x4, get under the truck and look at that harnesses that are close to drivetrain & axles....Look for harnesses that are hitting & rubbing.......This may save you a lot of time....
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Discretesignals
Ultimate Carjunky
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Feb 16, 2013, 12:57 PM
Post #7 of 10
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Re: 02 Envoy keeps blowing ETC #23 fuse
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 My Five Commandments of Control Module Replacement.
<choir singing in the back ground>
This is a list of things I made up that you should check before replacing any control module. You will never be 110% sure if a module is the problem even when you test all of its circuits, but your odds of success will be higher if those circuits are tested.
(1) check all power feed circuits with PCM powered up and or engine running (if able). Power feeds from battery and ignition switch circuits at PCM connector(s) should show battery voltage.
(2) check all ground circuits with PCM powered up and or engine running (if able). You should see less than 0.10 volts on any computer ground circuit to battery ground from PCM's connector(s).
(3) Check reference voltage supplies to sensors. This makes sure the reference voltages aren't shorted and taking down the PCM's power supply.
(4) Test all output devices. This means powering up solenoids, motors, relays, injectors, coils, etc. that the controller controls directly and measuring amperage on those circuits. This will tell you if there are devices that are using excessive amperage that can damage a PCM's driver circuitry.
(5) Inspect the PCM's connectors and plugs for bad terminal tension, pins that back out, corroded terminals/pins, contamination from oils, water, and/or coolant.
If you don't test this stuff and there are shorts in wiring or devices are shorted/worn and using excessive amperage, you'll probably toast your replacement PCM.
All the power, reference voltage, and ground checks have to be made at the PCM's connectors with everything plugged in. This means you will need to back probe the connectors.
Device checks are made by manually bypassing drivers. Most driver devices, except for fuel pump relays on GM, are ground controlled. Measure the amperage using an inductive clamp or connecting an amp meter in series. Always refer to the wiring schematic of a device circuit and technical description to see how the device is operated. You don't want to short power directly to a PCM's closed driver or you will be replacing the PCM.
Note: if there is a short or a device that uses a lot of amps and your using the amp function of a multimeter, it might blow the meter's fuse.
When you run your power and ground tests, you'll have to leave the ETC fuse out, but you will still need to test the devices associated with the ETC system.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Feb 16, 2013, 1:33 PM)
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speed
User
Feb 16, 2013, 1:28 PM
Post #8 of 10
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Re: 02 Envoy keeps blowing ETC #23 fuse
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Well i got as far as finding that pink wire goes in connector 3 as the ign 1 voltage circuit#839 pin 17 and comes out connector 1 as ign 1 circuit#439 pin 19
GM ASEP 26 SCC Milford ASE certified in Brakes and Electrical on Thursday April 5th 2012
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Discretesignals
Ultimate Carjunky
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Feb 16, 2013, 1:46 PM
Post #9 of 10
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Re: 02 Envoy keeps blowing ETC #23 fuse
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See this is problem. Once the power feed for ETC (pink) goes into the PCM, you don't know where it goes from there. It could be used to power the ETC circuitry in the PCM that is used to operate the ETC throttle motor or supply power to the power supply that feeds reference voltage to the TPS and APP sensors.
You don't know what happens to it when it goes in that dotted box unless you have service info that describes that circuit or there is a schematic floating around showing the inside of the PCM.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Feb 16, 2013, 1:47 PM)
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Discretesignals
Ultimate Carjunky
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Feb 16, 2013, 1:55 PM
Post #10 of 10
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Re: 02 Envoy keeps blowing ETC #23 fuse
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This is the ETC diagram. Don't see anything about the ETC fuse. But you can assume that somehow it is used to power the TAC motor and feed power supplies for sensors. I am making an educated guess. Who knows what the fuse does. It might be used for some other parts of the PCM or devices. How it is associated with C2 is unknown. Can theorize that when C2 is plugged in and the PCM has power, it powers up the ETC controls, but that is another edumacated guess.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Feb 16, 2013, 1:56 PM)
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