NEED HELP P1221 . engine power reduced

yazan

Original poster
Member
Jul 11, 2013
183
Hi. Just suddenly had this code.

I didnt reset untill now

Just an extra info. The headlights low neam some time shutting down with no reason. I removed the relay and re install it and give it a wiggle… and its working. But its happed again many times. So I swapped the relay with fan clutch relay and its working . so i put a used relay from junkyard in the hdm .

2 days ago I got some code about fan clutch circuit. And started with the relay. Swapped the relay with the hdm and its okay.


The 3 relays is working in the hdm but need to wiggle it some times or just push it down .

Is the fan clutch relay has something shared with this code!
 

Blckshdw

Moderator
Nov 20, 2011
10,665
Tampa Bay Area, FL
The 3 relays is working in the hdm but need to wiggle it some times or just push it down .

This sounds like the contacts inside the fuse block may not be making proper contact all the time. Maybe you can adjust them for a tighter fit?
 
  • Like
Reactions: yazan and mrrsm

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,642
Tampa Bay Area
For Diagnosing the P1516 and P1221 Codes:

Pull the Throttle Body Harness Connector OFF and push-pull on the wires to see if you can 'jiggle' any of them loose. Check the wiring along the Connector Pigtail for cuts, separations or any signs that any After-Market Wiring has been connected anywhere in the Engine Bay for Alarms, Remote Starters, etc. Get some CRC Electrical Circuit Spray Solvent and spray out BOTH the TB Connector insert and the TB Harness Connector and when they become completely bone dry.... plug them back together. Then Start the Vehicle at Idle and 'jiggle' the Harness-Pigtail wiring and see if the Engine 'shudders' or reacts to those movements. If it does... then either loose or broken harness wire is the probable suspect.

Plug in your OBD2 Scanner on and look at the PIDs for the ACC Pedal High and Low Voltage. Then...with the Engine OFF turn the Ignition Key to On-Run ...observe the OBD2 screen ACC Pedal PID Parameters while you step repeatedly down and up on the ACC "gas" Pedal. Record these changes in Voltage for BOTH the High and Low Circuits and let us know what you discover. My suspicions lean towards either a FUBARed Throttle Body Connector/Harness Pigtail problem...or an ACC Pedal Module problem.

Incidentally... The PCM's reaction to anything that MIGHT cause the Throttle Body to lose it positional reference and "Go to Wide Open Throttle..." accidentally required a Built-In Safety Measure to cause the Engine to Automatically go into a "Reduced Power Mode" by shutting off the Firing of at LEAST One COP (Coil On PLUG) reducing the number of cylinders available to "Make Power" from (6) down to (5)... preventing any "Runaway SUV" events from occurring. If the Throttle Position Sensor portion of the "Solid State" Throttle Body Internal Controls is Broken... the only solution will be to replace it. This is only one of a few other conditions that will cause a "Reduced Power" condition to set as a Code and trigger the same PCM Safety Response.
 
Last edited:
  • Like
Reactions: yazan

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Your fan clutch may be causing issues with your 5v reference circuit, which also feeds the throttle system. Unplug the fan clutch completely, not just the relay, clear the codes and see if the two codes stay off (you will likely get codes for the unplugged fan clutch). Check the wiring for chafing and shorting. Note that you might not be able to run the engine too long if your weather is hot and the A/C may not work well while unplugged.
 
  • Like
Reactions: yazan and mrrsm

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,642
Tampa Bay Area
The GM Factory Service Manual EV Fan Clutch Diagnostic Flow Chart:

FANCLUTCHGMDIAGNOSTICSCHART.jpeg

EVFC Diagnostic Instructions (Courtesy Eric "O" South Main Auto Channel)

EVFANCLUTCHWIRINGDIAGRAM1.jpg

Wiring Diagram of the EV Fan Clutch Circuitry:

EVFANCLUTCHWIRINGDIAGRAM.jpg

A Connector Pin Breakout of Relay #45 (Courtesy www.theroadie.org)

RELAY45CONNECTORBREAKOUT.jpg

TB/Envoy Power Distribution Center Fuses/Relays:

TRAILBLAZERPDC.jpg
 
Last edited:
  • Like
Reactions: yazan

TJBaker57

Member
Aug 16, 2015
2,897
Colorado
Speaking of fan clutches I added a new gauge to my torque app today. Fan Speed!! Woohoo that took me a while to dial in. Pid = 22162B, call it whatever you like, I used Fan Speed, units is of course RPM, scale is x1, equation is A*16, I set min at 0 and max at 2000, header at Auto.

All this is on a 2002 4.2 TrailBlazer. Hopefully works for others.
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,642
Tampa Bay Area
@TJBaker57 if you have more formulae like this excellent piece of information ... Can you do a New Topic Write Up about them over in the "Other Scanners" sub-forum, too? Many interested users of the Torque App may not read this particular Thread...and miss out...
 
  • Like
Reactions: yazan

yazan

Original poster
Member
Jul 11, 2013
183
oh so many rich info here , thanks all ,
really i dont know what i will do without @MRRSM @Mooseman , and @TJBaker57 its really good idea, i was always dreaming to have a tech2 to do many things , as doing a compare the actual and commanded fan speed

regarding to my problem , its now 3 days working fine after i swapping the hdm and fan relay ,
the first thing is that : mybe i have a problem in my fuse box !
because the headlights relay is ok but shaking it - or - reinstalling it will make the headlights to work again
also, before maybe a year , the compressor stopped working , i went to ac technician , we figured finally there is no commanded power in the compressor connector . so we jumped a wire from the fuse box (compressor fuse) , to the compressor , and its working now normally , on or off , its ok . so we think that time that the wire going from fuse box to the compressor is damaged somewhere

the second thing , also 2 years ago i got damaged fan clutch and the blade broken to peaces and it cut and damage every thing there , the radiator , the pipes and hoses , the belt, the hood , and sure : the fan clutch wiring harness in many places ! that really was a big mass there
so i ordered a Hayden fan clutch online from us (not available here) , and jumped to junk yards for the other parts, i replaced the fan wiring harness and the connector but i got confused that time because there is 2 gry wires , i search for the wiring harness , some one here told me just to try and see if there is any codes then swap the gry wires ,
yes there was a code then i swapped the gry wires and its ok since that time .

BUT in this time , some times the fan is engaging at full speed while driving specially when its hot outside, and some times not


so i will start with fuse box . but any ides or advises ?
 
Last edited:

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Sounds like a solid plan to check the fuse box. Check all the wiring that may have been damaged by the fan explosion before that may have been missed.

It is normal for the fan to speed up if it is hot outside, especially with the A/C running. I would imagine it gets really hot in your part of the world.
 
  • Like
Reactions: yazan

Forum Statistics

Threads
23,273
Posts
637,499
Members
18,472
Latest member
MissCrutcher

Members Online