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2001 - 2003 6.6L LB7 DURAMAX DIESEL WITH
MITTIE M. DRAGOSLJVICH
INITIAL VERSION:
UPDATE:
*IMPORTANT: THE FACTORY CRUISE CONTROL OPTION MUST BE PRESENT FOR THE HIGH IDLE SWITCH TO FUNCTION. PLEASE READ ALL OF THE INSTRUCTIONS BEFORE PROCEDING. IF THE CRUISE CONTROL OPTION IS NOT PRESENT, THE HIGH IDLE SWITCH MAY NOT FUNCTION, OR ONLY THE STANDBY SPEED WILL BE AVAILABLE. AN ADDITIONAL SWITCH OR SWITCHES FOR THE CRUISE CONTROL CIRCUIT MAY BE NEEDED. PLEASE READ THE SPECIAL CONSIDERATIONS CONCERNING THE PTO CONNECTOR.
SPECIAL
CONSIDERATIONS
1)
Poor
drivability will result if the high idle switch is left on when driving. The Duramax will accelerate poorly above ~
2200 RPM.
2)
The 2001
Duramax equipped trucks have three high idle speeds: STANDBY ~850 RPM, SET ~1250 RPM, and RESUME ~1700 RPM. The 2002 and 2003 trucks have only the SET and RESUME speeds available.
3)
In some
cases, the high idle option may need to be programmed using a Tech2 diagnostic
scanner before it will function.
4)
The STANDBY, SET, and RESUME RPM speeds can be
changed using the Tech2 diagnostic scanner.
5)
A
‘variable speed’ option exists for PTO/high idle operation and is visible with
the Tech2 scanner. Attempts at programming
the variable speed option on the 2001 and 2003 Duramax equipped pick-ups have
been met with limited success. The
variable speed option allows the user to ‘tap up’ or ‘tap down’ the idle speed in 100 RPM
increments using the RESUME (tap
up) or SET (tap down) buttons on the cruise control.
6)
The
variable speed option is available on the 3500 chassis cab models with the
factory RPO codes M1F and PTO. A
modified floor pan is part of those options.
RPO codes M1F and PTO are unavailable on the 2001 – 2003 2500HD/3500
pick-up platform due to clearance issues with the
floor pan used on these trucks.
7) Some of the 2500HD/3500 trucks have been manufactured with the PTO connector in place. The PTO connector (if present) should be located behind the airbag disable switch or behind the glove box on the passenger side. It is described as an 8-position connector taped up in one of the above locations.
8) If the PTO connector is present, a PTO accessory kit can be obtained from GM (part#12497678). The PTO accessory kit includes the PTO control switch, PTO interface cable, and instructions. The PTO interface cable is not utilized on the 2500HD/3500 pick-up platform since the interface connector located near the left side (driver’s side) PTO of the Allison 1000 transmission is not present. It may not be necessary to add the terminal/wire to the ECM connector C1-71 if the PTO connector is present in your truck. We are investigating the use of this connector to enable the high idle feature.
9) It is not known at this time if the high idle modification will work on 2003 Duramax equipped trucks with cruise control. It is rumored that the ECM terminal used on the 2003 Duramax for this features has changed. More experience is necessary to verify high idle operation on the 2003 Duramax vehicles.
10) UPDATED INFORMATION: Owners have reported successful installation of the high idle feature on MY 2003 Duramax equipped 2500HD/3500 pickup trucks using these instructions without any modifications. The same ECM terminal C1-71 is used for the high idle feature. The 2003 Duramax equipped trucks have only the SET and RESUME speeds available similar to the 2002 Duramax equipped trucks.
PARTS NEEDED:
1)
Terminal
GM part #12084913 (5 per package) or GM part #12084912 (10 per package) to add to the ECM at terminal
position C1-71.
2)
Fifteen
feet of 18 or 20-gauge wire. The length
of wire needed will be dependent on the location of the high idle switch. The color of the OEM wire for this circuit is
LIGHT
GREEN, but you can use
whatever color you have available. The
smaller 20-gauge wire is easier to work with and to add the terminal to the ECM
(Engine Control Module) connector. Another length
of similar gauge wire is needed for the 12V power lead.
3)
(1)
Single pole single throw switch (SPST) switch.
A simple toggle switch works well for this application. Fancier switches with dependent/independent
indicator lights can be used if desired but are not necessary, and require
basic knowledge of electrical circuits and wiring to hook up correctly. Since there are many different switching
options, these instructions will only cover using a basic SPST switch (toggle).
4)
Crimp
tool, connectors to attach the wires to your switch, fuse tap, 1A or 2A fuse,
and fuse holder. Soldered on connectors
may be used instead of crimp on connectors.
Split loom tubing, electrical tape, cable ties etc. as needed to clean
up the appearance of the installation.
5)
A small
amount of dielectric grease may be used on the added terminal for moisture
resistance.
6)
Access
to the factory shop manuals is recommended if unexpected questions or problems
arise during the installation. The GM
factory shop manuals can be purchased online from Helm Inc. at www.helminc.com
7)
A
multimeter will aid in installation, but is not required.
HIGH IDLE
INSTALLATION PROCEDURE:
1)
Disconnect
both batteries by unbolting the GROUND or NEGATIVE (-) cable from
each battery. IMPORTANT: The ignition switch must be OFF when removing
or reattaching the battery cables or damage to the ECM and/or TCM is possible.
2)
Locate
the Transmission Control Module (TCM) and the Engine Control Module (ECM). The TCM and ECM are
located on the driver’s side (DS) of the engine compartment (see FIGURES 1 and
2)
FIGURE 1: ECM and TCM LOCATION (Driver’s side of engine
compartment 2001 Duramax Diesel)
FIGURE 2: TCM LOCATION (Driver’s side of engine
compartment 2001 Duramax Diesel)
3)
The TCM is attached to the radiator shroud by
two 10 mm bolts. Removing the TCM allows
easier access to the ECM. Remove the two
10 mm bolts along the top edge of the radiator shroud and unplug the (2)
connectors from the TCM. The TCM will
remain attached to the cover. Lift up
and remove the TCM/TCM cover and place them in a safe location to avoid damage. Handle the TCM carefully and avoid dropping
it to prevent damage.
4)
Remove the ECM cover. The black plastic ECM cover comes off by
releasing two tabs, one tab near the top edge of the cover located rearward,
the second tab is on the front lower edge
which is hard to get to (and see).
Release the top rearward tab first by reaching between the battery and
the radiator hose, and pressing very hard. The front lower tab will then
release easily. The ECM plastic cover is a tight fit, but will come out. Release
the plastic wire loom clip(s) attached to the cover so the ECM cover can be
removed.
5)
Access
to the ECM connectors is made easier by releasing the metal spring latch and
the plastic tabs holding the ECM in position.
6)
You
should be able to see the two 80 pin ECM connectors, C1 (blue) and C2 (red).
The blue C1 connector faces the passenger side (PS) of
the truck and blue may be marked on that side of the ECM. There
is a small red area on the top of the DS connector; this is
the red C2 connector.
7)
There is
a small bolt in the middle of each ECM connector that holds the connector to
the ECM. Remove the bolts from the center of each ECM connector C1 and C2. Unplug the ECM connectors C1 and C2 and remove the ECM from the engine compartment. Handle ECM carefully and avoid
dropping it to prevent damage. Place
the ECM in a safe location.
8)
Identify
the blue C1 ECM connector. Release the tabs on the wire end of the
connector for access to the back of the connector.
9)
There
are small numbers printed on the connector body to identify the terminal
positions. Locate terminal position C1-71 and place a small mark on the connector to
facilitate identification of this position. C1-71 is the position to add the terminal for the high idle for the Duramax
diesel. For reference, terminal position
C1-70 should have a BROWN wire in place.
Terminal position C1-72 is empty (at least on 2001 models), and C1-73
should have a BROWN/WHITE wire in that position. The colors of the wires referenced for C1-70,
C1-72, and C1-73 are from MY2001 and may be different for the MY 2002 – 2003
vehicles.
10)
Prepare
the terminal (GM part #12084913 or #12084912) that will be added to the ECM
connector C1-71 by crimping or
soldering the terminal to 18 or 20-gauge wire.
Using smaller 20-gauge wire will make adding the terminal to the
connector easier. If solder is used to
attach the terminal to the wire, use sparingly and avoid clumping the solder
since it will be difficult to properly seat the terminal in the connector
body. Apply a small amount of dielectric
grease to the wire terminal. The OEM
wire color for this circuit is LIGHT GREEN, but any color wire can be used.
11)
Using a
small pick or other sharp object, puncture the YELLOW insulation from the wire side of the blue C1 ECM connector to correspond to the C1-71 position.
12)
Remove
the translucent plastic cover over the terminal ends of the ECM blue C1 connector by releasing the tabs on each end.
13)
Insert
the terminal you prepared above (with wire attached) from the wire side of the blue C1 connector position C1-71.
14)
VERY IMPORTANT: Make sure the terminal goes all the way to
the edge of the ECM connector to insure proper contact. Use the existing terminals as a guide.
15)
Replace
the translucent plastic cover over the terminal ends and reassemble the cover over
the wire end of the blue C1
connector. Carefully inspect the
reassembled ECM C1
connector to make sure all terminals are in the proper location.
16)
Route
your added wire as desired toward the firewall.
Use split loom tubing, electrical tape, and cable ties as needed for an
OEM appearance.
17)
Reattach
the blue
C1 and red C2 ECM connectors to their proper location on
the ECM. The proper torque valve for the
ECM connector bolts is 8 N•M or 70 lb -in. DO NOT OVER TORQUE or damage to the ECM and/or ECM connectors could result.
18)
Reattach
the ECM and TCM to their proper locations.
Remember to plug in the (2) TCM connectors, and attach the TCM using the
two 10 mm bolts.
19)
Find a
place on the firewall to run the added wire into the cab. On the Duramax diesel, a good location is
pictured below:
FIGURE 3: FIREWALL ACCESS FOR WIRING (2001 Duramax
Diesel)
You can
also pierce the rubber boot for the main wire harness entry into the cab
located below the hydroboost assembly and run the wires into the cab.
20)
Find a suitable location in the cab to mount
the high idle switch. The metal lip
along the bottom of the instrument panel offers a good location to mount a
toggle type switch.
21)
Find a 12V source. A fuse tap can be used to obtain switched 12V
power from the fuse panel accessible when the driver front door is opened. It is recommended to use an in-line fuse (1A
or 2A) on this 12V power lead as a precaution.
If you want to interface the high idle switch with an aftermarket remote
start system, you will need to locate an unswitched 12V source for this
step. Suggestions for an unswitched 12V
power source include direct wiring to the battery, the wiring harness in the
steering column, or the fuse panel on the passenger side accessible when the PS
front door is open.
22)
Route
the 12V power lead and the high idle wire to your switch location and attach
the wires to your switch.
23)
Double-check all the wiring and
connections. Make sure the wires do not
interfere with the normal operation of any vehicle components, and will not be
pinched or crushed.
24)
Reattach the battery cables. IMPORTANT: The
ignition switch must be OFF when removing or reattaching the battery cables or
damage to the ECM and/or TCM is possible.
HIGH
IDLE OPERATION
1)
Start
the truck normally using the ignition key.
If using a remote start, the high idle may not work unless a 12V
unswitched source was used as the power lead to the high idle switch.
2)
Set the
parking brake. The parking brake MUST be
set in manual transmission equipped trucks.
3)
Transmission
should be in PARK or NEUTRAL for Allison equipped trucks.
4)
Transmission
must be in NEUTRAL for the 6 speed manual equipped trucks.
5)
Vehicle
speed must be 0 MPH.
6)
The
brake pedal or clutch pedal is not depressed.
7)
Turn on
the high idle switch.
8)
Turn on
the cruise control switch.
9)
The idle
speed will increase to the STANDBY
speed of ~850 RPM for 2001 Duramax
diesel equipped trucks. If you have a
2002 or 2003, you MAY NOT see an increase in the idle speed to 850 RPM at this
time.
10)
Hit the
cruise control SET button.
The idle speed will increase to ~1250 RPM for 2001 - 2003 Duramax
equipped trucks.
11)
Engage
the RESUME switch on the cruise control stalk. The idle speed will increase to ~1700 RPM for
2001 - 2003 trucks.
12)
If the
Duramax engine is cold, it may take a few seconds to a few minutes for the high
idle to engage. This is normal
operation. Some have reported that it
may take a few minutes for the high idle to engage when used for the first time.
13)
Stepping
on the brake pedal, clutch pedal, or shifting into gear will turn off the high
idle. If the brake pedal or clutch pedal
is released, the high idle speed will resume.
14)
Shifting
the Allison back into PARK or NEUTRAL will resume the high idle speed.
!!!!REMEMBER TO TURN OFF THE HIGH IDLE SWITCH BEFORE DRIVING
THE VEHICLE SINCE POOR DRIVABILITY CAN RESULT.
THIS IS DESCRIBED AS POOR ACCELERATION OR ‘MISSING’ ON ACCELERATION
ABOVE ~2200 RPM!!!!
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