Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner
1 - 12 of 12 Posts

·
Registered
2002 gmc envoy_slt
Joined
·
8 Posts
Discussion Starter · #1 ·
I've got an 2002 Envoy with 94000 miles on it that has been battling the service engine soon, reduced engine power problem for better than a year now. It started just happening every once in a while, code reader gave code for throttle pedal so i replaced that and it seemed to go away. But it returned about 2 months later and i was just living with it. Since then it has progressed into a daily problem , pulling over shutting it off restarting and continue on my way. But now 4 days ago it won't even start unless you hook a scan tool to it and clear the codes(P1221 P1516 P1223) but as soon as you shut if off or it just dies you can't start it with out clearing the codes. So i ordered a new throttle body/tps sensor installed it and still no luck. I went down to local dealer they said to solider all the pins where they are crimped they claimed they've seen issuse with them so i did so and still no start. I've run out of ideas to solve this issue. Anyone with some ideas i'm all ears.

The codes i most commonly get are P1221 P1516 but occasionally get P1223 and just once i had P1275 and P1280 added to the rest. And evevn when the codes are cleared the P1221 never goes away it right back in there before you restart it.
 

·
Banned
2004 gmc
Joined
·
26,181 Posts
FOund this in a Google search. May be possible to see broken wire insulation in the vicinity of the fan clutch. And temporarily, just unplug it.

The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.
Condition/Concern:
Reduced power light on and DTC P1680 P1221 and/or P1271 stored in the PCM
Recommendation/Instructions:
Monitor the 5V reference to the Accelerator Pedal Position ( APP ) sensor, circuit 1274, using Peak Min/Max on a Fluke 87. Refer to Si document 1454678 for the 5V reference schematics. Command the fan clutch control "on" with the Tech 2 at 50%. If when commanding the fan clutch on, the 5V reverence spikes to battery voltage, the concern is the 5V reference shorted to battery voltage intermittently inside cooling fan clutch. Replace the fan clutch to repair this concern.
.
Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.
Models:
(02 - 05 Chevrolet Trailblazer and Trailblazer EXT) and (02 - 05 GMC Envoy, Envoy XL and Envoy XUV ) and (02 - 05 Buick Rainier) and (02 - 04 Oldsmobile Bravada)
 

·
Registered
2002 gmc envoy_slt
Joined
·
8 Posts
Discussion Starter · #3 ·
I can't belive it!! I unplugged the harness and it starts right up. All they old codes disapear, the only one i got now is P1481 for the fan being unhooked. I ordered new fan cluth and harness from local Napa hopefully have this thing fixed tomorrow. Is it possible its just the harness that needs repaired/replaced? And if i replace the whole clutch do i really need to have the computer updated??
 

·
Banned
2004 gmc
Joined
·
26,181 Posts
That's why I advised to loose closely at the harness for chafed wires. If you've never been reflashed at the dealer, you can gain some better start-up AC performance with new software driving the fan, but the new fan in and of itself doesn't need any new software to run.

Oh, I wish I was charging money for these Hail Mary diags. :woot:
 

·
Registered
2002 gmc envoy_slt
Joined
·
8 Posts
Discussion Starter · #6 ·
Well the reduced engine power problem has returned.. I haven't gotten around to taking it to my local shop to get the codes out yet but it does seem to happen alot les than before but still not right.. The local gm dealer doesn't seem to have a clue.. Is the fact that i haven't gotten the update done causing my problems? I really don't wanna pay the insanely high priced dealer $90 per hour to tell me that didn't fix it..
 

·
Banned
2004 gmc
Joined
·
26,181 Posts
Can't tell a thing without the code. Assume you changed the harness and fan clutch when you said you were going to?
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
997 Posts
Some more ideas:

Are you still running on the original battery? Have you had your battery load-tested recently?

Have you replaced the ignition switch yet?

If the voltage drops below 5 volts, the crankshaft position sensor loses its reading and the engine reduces power and becomes hard to start. This could be caused by the wiring harness as Roadie suggested, but could also be a battery problem or an ignition switch problem. (The ignition switch is very common with our vehicles and causes a host of seemingly unrelated or random symptoms, but thankfully is easy to repair.)
 

·
Registered
2002 gmc envoy_slt
Joined
·
8 Posts
Discussion Starter · #9 ·
The codes

Well the codes i got are P0014B cam sensor and P1271A throttle pedal sensor.. And yes i replaced the fan and harness and it was all good for bout a week or so.. And yes I replaced the ignition switch about 2 years ago and the battery around the same time.. I've replaced the throttle pedal twice now because i keep getting that code.. If i just truely need to replace the cam sensor thats fine i'm just really sick of replacing parts that the computer say is bad and its a totally unrelated issue..
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
997 Posts
Sorry but I cannot help but think it's still a wiring or voltage issue. I think those sensor codes are merely symptoms and not causes.

I wonder if your replacement ignition switch is now going bad?
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
997 Posts
I would change out the ignition switch again, just to be sure. There are great tutorials on how to do that here.
 
1 - 12 of 12 Posts
Top