19 09 GM Invalid Torque Signal

TECHNICAL SERVICE INFORMATION
GENERAL MOTORS
INVALID ENGINE TORQUE SIGNAL
COMPLAINT: In this example, a 2007 Pontiac Solstice with 2.4 Liter engine and 5L40E transmission
has a complaint of a harsh shift. The scan tool reveals that DTC P2637 is set for an
Invalid Engine Torque Signal being sent to the TCM from the ECM. This was the only
stored code at this time. There was a previously stored code of P0171 for Fuel System
Lean, but was not present at this time.
NOTE: The torque reduction request is sent to the ECM through the CAN
communication network. If the TCM receives a torque reduction failure message
from the ECM, the torque signal DTC will be set. A fault in the CAN system will not cause
a torque reduction signal code.
The engine was running fine and the ECM and the TCM were both replaced yet the
complaint would return after one mile of driving.
CAUSE: Realizing that there are many faults that can generate a torque signal failure
message, when it was learned that this vehicle had once stored P0171 for Fuel
System Lean, the scan tool was set to display the Fuel Trim Data. The Long Term Fuel
Trim (LTFT) indicated +20 which means the ECM is adding fuel supply to the engine to
try and compensate for what the ECM perceives to be a lean running condition,
therefore, it was decided to inspect the fuel system. It was then noticed that the fuel
had an unusual odor and feel.
The technician connected a container of fuel to the fuel rail, bypassing the vehicles
fuel supply and ran the vehicle on this fuel supply.
On the test drive the complaints disappeared instantly! The P2637 did not return and
the harsh shift condition was gone. The cause of these complaints was the use of E85
Ethanol fuel (figure 1), in a vehicle that was not designed to use E85. This is indicated
on the Vehicle Emission Control Information sticker located in the engine bay as seen
in figure 2.
CORRECTION: The fuel tank was drained and refilled with straight gasoline and the vehicle
performed normally.
SERVICE INFORMATION:
To determine how much Ethanol by percentage is in the fuel tank, a 50 millimeter
sample of the vehicles fuel will require testing. A 100 millimeter graduated test tube
will be needed to perform this test.
Continued
19-09
AUTOMATIC TRANSMISSION SERVICE GROUP Page 1 of 4
GENERAL MOTORS
SERVICE INFORMATION Continued:

Start by filling the test tube with 50 millimeters of water, then pour in the 50 millimeters
of fuel (see figure 3).
Mix the solution by shaking it and then let the mixture settle until a distinct separation
can be seen. This will occur due to the fact that gasoline will float on top of the water.
Ethanol will mix with water which is why a dividing line develops in the test tube. The
location of the separation above or below the 50 millimeter mark depends on how
much Ethanol is in the fuel.
Count the number of graduated millimeters that are above the original separation of
the 50 millimeter mark. The example shown in figure 3 shows that to be 16 millimeters
above the 50 millimeter line.
Multiply 16 by 2 which equals 32, this means there is 32% Ethanol in the fuel tank
which would cause the complaints listed above when used in a vehicle that is not
designed for Flex Fuel use.
Using E85 Fuel requires an increase in the fuel system's ability to feed the engine 45%
more fuel at WOT than when using conventional gasoline fuel. This means higher
volume fuel pumps are needed as well as larger fuel lines. This also means it needs
adequate fuel pressure regulators along with higher capacity fuel injectors.
Especially if it is being used in high performance applications.
E85 Fuel should ONLY be used in a Flex Fuel compatible vehicle. Items that must be
avoided in the fuel system are:
1. Mild Steel
2. Standard Rubber Compounds
3. Copper Components
4. Non-Anodized Aluminum
5. Zinc and other soft metals
The above mentioned items when used with E85 fuel will corrode or severely
deteriorate.
Flex Fuel built vehicles are designed to use higher levels of Ethanol by using materials
compatible with E85 Fuel.
19-09
GENERAL MOTORS
Copyright © 2018 ATSG
Figure 1
H1101197
Figure 2
19-09
GENERAL MOTORS
ETHANOL TESTER
50 Milliliters
of fuel
50 Milliliters 30ml 30ml
of water
100 100
90 90
80 80
16 Milliliters
above 50 Milliliters
70 70
60 60
50 50
16 x 2 = 32% ETHANOL
Figure 3
19-09

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TECHNICAL SERVICE INFORMATION

SERVICE INFORMATION Continued:

Copyright © 2018 ATSG

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