Bought a 2008 Hummer h3 3.7 a month ago as a project had a blown motor it was sitting for about 3 years and previous owner already had things apart. I picked up a 2008 canyon with a good 3.7 engine did the swap and now it will not run right at all or flat out just not start says 'Reduced power' on dash it turns over fine. I cleared codes many times and the ones that instantly come back are 'p0689-00 Engine control igniton relay feedback circut low voltage' 'p1682-00 ignition 1 switch circut 2' I have swapped out relays fuses checked em all no where is it clear what relay this is talking about. I have been screwing with this dam truck for a week at my wits end. Should I replace the ignition switch or do you think the relay code is the issue?. Also another thing to note I have noticed the throttle blade does not move no matter what swapped out throttle bodys aswell had a few laying around but someone told me that is part of the 'reduced power' failsafe the throttle blade stays in one spot?

Any help would be appreciated before I sell this thing and cut my losses.

 

 

ok thanks I did have some corroded pins on 1 or 2 relays but where un related to ingnition that I cleaned up I will remove the whole box tomorrow take it apart and inspect.

 

New fuse box installed Still the same god dam code where do i go from here lol runs terrible little to no throttle response.

 

The throttle has no response the blade does not move at all even when commanded tried 3 throttle bodys Or is this a symptom when it goes into reduced power?

 

What causes the P0689 code?

A faulty PCM relay is the most common reason for the storage of a P0689 trouble code. Some other common causes include:

• a defective PCM,
• bad battery, corroded or damaged battery cables or cable ends
• shorted or open circuits, a bad fusible link, or a blown fuse

What are the symptoms of the P0689 code?

Various symptoms can come about due to P0689 trouble code and range from just the illumination of the Check Engine Light to the vehicle not starting at all. The mechanic should keep in mind that if the PCM relay is defective that the Check Engine Light might not come on at all.

 

How does a mechanic diagnose the P0689 code?

While a P0689 trouble code is most commonly caused by a faulty ECM/PCM power relay sense circuit, a mechanic should fully diagnose the system to make sure another component, such as the PCM itself, is not at fault. To diagnose a P0689 trouble code requires the use of an advanced scanner, manufacturer's wiring schematic, and a digital volt/ohmmeter. The mechanic must also perform the following diagnostic steps:

• Begin by inspecting the battery, battery cables, and battery cable ends.
  
• Test the fuses and fusible link for fault.
  
• Using the manufacturer's wiring schematic, carefully inspect all wiring, connectors, and components dealing with the PCM.
  
• Clear the code and test the system to see if it returns, making sure to test drive the vehicle.
  
• If the code returns or the vehicle does not start, unplug the PCM relay connector and test for reference voltage and ground signals, comparing them to the manufacturer's specifications.
  
• The mechanic should make sure to unplug the PCM and all other related modules before probing the circuits to avoid damage and control module memory loss.
  
• Inspect the PCM to make sure it is not faulty.
  

*Clear the trouble code before retesting the system to see if the code returns.

Common mistakes when diagnosing the P0689 code

A common mistake made by mechanics when diagnosing a P0689 trouble code is to replace the PCM when it is in fact not faulty. This is an unnecessary repair/replacement that results in the return of the trouble code because the relay, which is actually at fault, still remains.

How serious is the P0689 code?

If left unfixed, the problems associated with a P0689 trouble code can lead to the vehicle not starting. The Check Engine light can also fail to illuminate when the PCM stores a P0689 trouble code due to a fault in the PCM.

What repairs can fix the P0689 code?

To repair a P0689 trouble code, the mechanic should perform the following:

• Replace the battery if it is bad
  
• If the battery cables have damage, such as cuts or are kinked, replace them as well
  
• The battery cable ends should also be free of damage or corrosion. If corrosion is present, clean the clamps. If damaged too much, replace the battery cable ends
  
• Make sure that the battery is fully charged
  
• Replace any faulty fuse or fusible links
  
• Replace any faulty or damaged PCM wiring, connectors, or components, including the ECM/PCM power relay sense circuit
  
• Replace the PCM/ECM if faulty
  

 

Theres the gibberish from a quick web search on google. Lol! the real work now begins because your gonna wanna figure out using a service manual which wires feed each of the mentioned items and the probe them for continuity or use a test light to test there integrity.

 

trace the harness loom from the throttle body they tend to disintegrate close to corner bends the wires might be frayed

 

Ok thanks guess I am really going to have to dig in now.. I didnt see anything obvious but il have to start un doing the loom. Also noticed today there is a questionable looking autostarter and aftermarket radio installed going to remove/fix those first as Ihave never personally seen this truck run good but it must of been running normal when the motor blew so sometime between the other guy removing the other motor and me putting this one in something happened.