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Discussion Starter · #1 ·
My aunt has an 03 TB that died while driving the other day. It will crank over but won't start, not even a catch. The towtruck driver told her that it was the fuel pump so she bought one and asked me to replace it. I can hear it priming when I key on, so I relieved all pressure from the schrader valve at the filter (while it was off of course), then keyed on and off and checked the valve again - plenty of gas sprayed out. So I assumed that the pump is fine.

My brother came up with a scan tool and we got 6 codes, one for each injector. I can't remember the exact phrasing or code but the diag tool said something like 'Injector circuit malfunction'

We erased the codes - no luck. we disconnected the battery - no luck. we unplugged the 3 PCM harnesses to check for corrosion - none. I would have checked the injector plugs but I can't even see the dang things. Do you need to remove the intake to get to them?

So does anyone have any clue what is wrong with this? On certain other non-GM vehicles the ASD (auto shut down) relay may cause this problem, but usually it will also prohibit the fuel pump form initial priming. Any ideas?

Thanks!
 

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I'd guess a PCM problem, or a blown fuse 28 under the hood that feeds all six injectors.

Tow truck drivers are only one step up from parts counter staff when it comes to advanced troubleshooting skillz. :rolleyes: :hopeless :bonk:
 

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Discussion Starter · #3 · (Edited)
yeah I forgot to mention that I checked all the fuses in the box under the hood. I even used my multimeter on them just to be sure!

Once I heard that it was the tow truck driver that diagnosed the problem I decided to check it out myself before I started to drain the tank!

Reading through the forums, I see that these have issues with the ignition switch. Could it be that?
 

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Discussion Starter · #4 ·
UPDATE!
ok, I went up to my Aunt's yesterday to fix the ignition switch. I took the old one out and opened it up and tested it - everything checked out OK and all of the contacts looked fine, no corrosion, signs of arcing or anything like that. It looked brand new. I installed the new one anyway. No luck there. I checked for fretted/worn wiring underhood as in this post: http://forums.trailvoy.com/showthread.php?t=44214&highlight=cranks+start&page=4 but I couldn't find anything wrong. Pulled all of the fuses again and all of the fuse contacts seemed fine. The injectors still aren't firing. I tested spark just to rule it out and #2 had spark (the only one I checked), so I put it back in with a little starting fluid, squirted some more starting fluid in the throttle body and it fired up. It would only stay running with the starting fluid though, it was getting no gas. I can hear the fuel pump kick in and I can feel the relay click when I turn the key, and the line has pressure in it. Is there one master signal wire that could be damaged somewhere that would kill all 6 injectors, or is it just time to change the PCM and move on?
 

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You could check the pink wire going to each of the injectors for 12V, which comes straight from fuse #28 as I mentioned. The PCM controls all six injectors directly, but there are other conditions under which they would be inhibited, like a passlock key cylinder security malfunction.

Do you see the security light illuminated on the dashboard?

The security system is managed by the BCM, which sends a data link message to the PCM to enable fuel delivery. Might be time for the dealer to look at the security system.
 

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Discussion Starter · #7 ·
Someone my aunt talked to mentioned that the crank sensor might be bad. Wouldn't that send a fault code though? The only fault codes I got were for each of the 6 injectors. It is supposedly a pretty cheap part though. like $20 or something, but even that cheap I still hate throwing parts at a problem.
 

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Discussion Starter · #8 ·
Okay, I've got more info. I located the pink wire on the main injector harness connector (located near the #5 coil) and tested voltage. It was reading between 5.3 and 6.5 volts, the voltmeter just floated in between those values. Fuse #28 is good and has 12 volts to both sides of the fuse (with the fuse disconnected). Is it supposed to get 12 volts at the pink wire? If so then I can put a jumper to there and try to start it, but if it is supposed to get only ~6 volts then I'll cook something.

I read the codes again, they are
P0201 - Injector Circuit Problem Cylinder #1,
P0202 - Injector Circuit Problem Cylinder #2,
and so on.

No other codes.
 

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The pink is supposed to be at a full 12V. With the fuse out, there's no current flow, so a high resistance somewhere in the circuit isn't going to drop any voltage and that's why it looks OK.

See if you can monitor the fuse voltage with it installed, such as with an add-a-tap gadget.

The high side of the fuse is actually connected to the RUN/START bus coming from the ignition switch, not straight to the 12V battery bus, but I bet you found that out already.

You might also have a high resistance connection from the coil side of the fuse to the injectors. There's some redundancy in the wiring to the injectors (three connector pins in the harness at the fuse block, each one feeding two injectors). All I can think of is a bad fuse socket right now. OK with no load, but can't run an injector without dropping voltage down to what you measured. A shorted coil or wiring harness would blow the fuse.
 

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Discussion Starter · #10 ·
So do you think that I'd be ale to run a jumper lead from the pink wire at the main injector harness to a known 12v source? Would that mess anything up as long as I don't connect it while the key is off (I wouldn't want to back feed anything that shouldn't have power while keyed off)?

Thanks!
 

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Discussion Starter · #12 ·
My aunt decided to by a computer and give that a try. I went up there again and played around some more with the injector harness.The battery was down to 11.5volts (I had done alot of cranking with it)and I was getting like 9 at the injector feed this time. I checked the resistance of all the injectors just to be sure, they were all within spec. I hooked a running vehicle up to it (to get 13.8 volts) just to make sure I had plenty of juice, and at that point I was getting about 11 v at the pink injector feed wire. I tried to start it and whadya know, it caught! Very briefly though, only fired a couple times. I got it to catch a few more times, then once I was able to get it to rev up to about 3 grand before it died.
I forgot to try the direct lead to the injectors, I had other **** to fix too. I'll have to do that next time. I did try the computer anyway. The documentation that came with it told me to start it, let it die and wait for the security light to come on to program the key or something. It wouldn't even crank. Put the old one back in and it would catch a little like before. Weird - maybe I missed something I was supposed to do to initialize it.
 

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Discussion Starter · #13 ·
So splicing a wire in worked fine, it fired right up. I just took a lead out from the #28 fuse (with the fuse still in) and spliced it into the pink wire at the injector harness. Now I guess I should try to find a junkyard fusebox and replace the whole thing.
 
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