NEED HELP 2005 GMC Envoy 5.3 invaded by gremlins

Rumblefish

Newbie
Original poster
Jan 4, 2016
3
Oklahoma
I have been having a problem with my 2005 Envoy 5.3 for over a year now. I get multiple codes including p0443, p1682, p1516, and p0689. I recently had my fill and paid a mechanic to come out and diagnose the rig. It started with intermittent stalling and after 20-30 min break would start again. Then went to intermittent starts setting off the reduced power trouble light. I replaced the throttle body and the map sensor which cleared up the throttle delay and reduced power light. Now it will start fine and run for exactly 37 min and just die. No start after that for at least 3hours. I'm losing my patience with this thing. Please help me figure this thing out. I've started this thing several times today and it runs great for 35-40 minutes then falls flat on it's face. Any ideas about repairs would be greatly appreciated.
 

Mounce

Guru
Mar 29, 2014
13,667
Tuscaloosa, AL
I'd start with tracing the wires from the throttle body to the pcm as you have multiple codes pointing towards discrepancies on throttle position.

Possible cause I saw for the p1682 was faulty ignition switch, the switches are notorious for going bad on our rides so it might not be a bad idea to throw one of those in as well.
 

dmanns67

Guru
Apr 3, 2013
32,979
Ohio
Is all the mechanic did was replace the TB and map sensor? Did the new TB and MAP sensor take care of the P1516 code or all codes listed still there?

P0443 is related to EVAP Canister Purge Valve Circuit Malfunction which could mean your purge valve is not operating properly for your fuel system. Common issue on the TB either with the purge valve on the engine or solenoid valve on the gas tank.

P1682 Charging System Voltage Too Low. I have had my battery light come on the dash before indicating the charging system voltage was too low, but never a P code. Turned out my battery CCAs were less than half of a battery that is in good health. Would not be a bad idea to load test your battery and have the alternator checked.

P0689 Engine Controls Ignition Relay Feedback Circuit Low. Almost sounds like the ignition switch to me as like Mounce stated, those are known to go bad, but could also be related to the charging system voltage issue.
 

Rumblefish

Newbie
Original poster
Jan 4, 2016
3
Oklahoma
Is all the mechanic did was replace the TB and map sensor? Did the new TB and MAP sensor take care of the P1516 code or all codes listed still there?

P0443 is related to EVAP Canister Purge Valve Circuit Malfunction which could mean your purge valve is not operating properly for your fuel system. Common issue on the TB either with the purge valve on the engine or solenoid valve on the gas tank.

P1682 Charging System Voltage Too Low. I have had my battery light come on the dash before indicating the charging system voltage was too low, but never a P code. Turned out my battery CCAs were less than half of a battery that is in good health. Would not be a bad idea to load test your battery and have the alternator checked.

P0689 Engine Controls Ignition Relay Feedback Circuit Low. Almost sounds like the ignition switch to me as like Mounce stated, those are known to go bad, but could also be related to the charging system voltage issue.

I have already changed the ignition switch, tested the alternator, and checked the battery. I am currently in the process of tracing wire as a lot of the codes pertain to voltage but have not found anything yet. My mechanic only diagnosed the throttle body, I had to figure out the map sensor myself.
 
Last edited by a moderator:

Mooseman

Master Blaster
Moderator
Dec 4, 2011
22,763
Ottawa, ON
That p1682 certainly points to a voltage issue to one of the circuits to the PCM and p0689 as well. I'd be checking the wiring to the PCM and possibly the PCM itself or the wiring to/from the ignition switch. Where it's located, I wouldn't be surprised if there is corrosion in the connector.
 

gmcman

Guru
Dec 12, 2011
4,576
Is your alternator putting out the correct voltage? Check voltage with engine off, then idling, then raise rpm and it may increase a little.

What work was done prior to all your troubles?

I would take some electronics cleaner and clean out the wiring harness on the MAF and the TB.

Have you cleaned your MAF? If so, what did you use to clean it?
 

mrrsm

Lifetime VIP Donor
Oct 22, 2015
6,123
Tampa Bay Area
Another confirmation Video:


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