
Symptom:
IC CAN MESSAGE INCORRECT
When Monitored and Set Condition:
IC CAN MESSAGE INCORRECT
When Monitored:
Set Condition: CAN Bus messages received from the Instrument Cluster are incorrect.
POSSIBLE CAUSES
CAN BUS CIRCUIT DTC PRESENT
INSTRUMENT CLUSTER DTCS PRESENT
OPEN CAN CIRCUITS AT INSTRUMENT CLUSTER
INSTRUMENT CLUSTER
TEST ACTION APPLICABILITY
1NOTE: Low fluid level can be the cause of many transmission problems. If
the fluid level is low locate and repair the leak then check and adjust the
fluid level per the service information.
NOTE: Always perform diagnostics with a fully charged battery to avoid
false symptoms.
With the DRBIIIt, read the engine DTCs. Check and repair all engine DTCs prior to
performing transmission symptom diagnostics.
With the DRBIIIt, read and record all Transmission DTCs.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal
connections can set DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Repair as necessary.
Most DTCs set on start up but some must be set by driving the vehicle such that all
diagnostic monitors have run.
Note: Verify flash level of transmission controller. Some problems are
corrected by software upgrades to the transmission controller.
NOTE: Check for any Technical Service Bulletins that may apply.
Perform this procedure prior to Symptom diagnosis.All
Continue
Go To 2
2 Ignition on, engine not running.
With the DRBIIIt, read Transmission DTCs.
NOTE: If the DTC, CAN BUS CIRCUIT, is present, perform diagnostics on
that symptom first.
Is the DTC, CAN BUS CIRCUIT, present?All
Ye s!Refer to the Transmission category and perform the appropriate
symptom.
No!Go To 3
70
TRANSMISSION - NAG1

Symptom:
IC/ATC CAN MESSAGE MISSING
POSSIBLE CAUSES
CAN BUS CIRCUIT DTC PRESENT
AUTOMATIC TEMP CONTROL DTCS PRESENT
INSTRUMENT CLUSTER DTCS PRESENT
OPEN CAN BUS CIRCUITS AT INSTRUMENT CLUSTER
OPEN CAN BUS CIRCUITS AUTOMATIC TEMP CONTROL
AUTOMATIC TEMP CONTROL
INSTRUMENT CLUSTER
TEST ACTION APPLICABILITY
1NOTE: Low fluid level can be the cause of many transmission problems. If
the fluid level is low locate and repair the leak then check and adjust the
fluid level per the service information.
NOTE: Always perform diagnostics with a fully charged battery to avoid
false symptoms.
With the DRBIIIt, read the engine DTCs. Check and repair all engine DTCs prior to
performing transmission symptom diagnostics.
With the DRBIIIt, read and record all Transmission DTCs.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal
connections can set DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Repair as necessary.
Most DTCs set on start up but some must be set by driving the vehicle such that all
diagnostic monitors have run.
Note: Verify flash level of transmission controller. Some problems are
corrected by software upgrades to the transmission controller.
NOTE: Check for any Technical Service Bulletins that may apply.
Perform this procedure prior to Symptom diagnosis.All
Continue
Go To 2
2 Ignition on, engine not running.
With the DRBIIIt, read Transmission DTCs.
NOTE: If the DTC, CAN BUS CIRCUIT, is present, perform diagnostics on
that symptom first.
Is the DTC, CAN BUS CIRCUIT, present?All
Ye s!Refer to the Transmission category and perform the appropriate
symptom.
No!Go To 3
3NOTE: NOTE: If vehicle is equipped with Air Conditioning diagnose the ATC
system first.
Is the vehicle equipped with air conditioning?All
Ye s!Go To 4
No!Go To 6
72
TRANSMISSION - NAG1

Symptom:
IMPROPER GEAR
When Monitored and Set Condition:
IMPROPER GEAR
When Monitored: Engine RPM greater than 450 and output speed (ABS) greater than
180 RPM. No Input Speed sensor N2 - N3, Shift lever, and/or ABS wheel speed DTCs
present.
Set Condition: The TCM compares the calculated gear with the gear the transmission
has actually engaged. If the actual gear differs from the gear calculated by the TCM, the
TCM value is adjusted to the engaged gear and a counter is increased by 2. If after a shift
the engaged gear and the calculated gear still match , the counter is decreased by 1 point.
A DTC is detected as soon as the counter exceeds a threshold. If the fault is detected 3
consecutive ignition cycles the transmission will be placed in Limp-in and the MIL
activated.
POSSIBLE CAUSES
ABS DTCS PRESENT
SOLENOID DTCS PRESENT
INTERNAL TRANSMISSION
TCM - IMPROPER GEAR
TEST ACTION APPLICABILITY
1NOTE: Low fluid level can be the cause of many transmission problems. If
the fluid level is low locate and repair the leak then check and adjust the
fluid level per the service information.
NOTE: Always perform diagnostics with a fully charged battery to avoid
false symptoms.
With the DRBIIIt, read the engine DTCs. Check and repair all engine DTCs prior to
performing transmission symptom diagnostics.
With the DRBIIIt, read and record all Transmission DTCs.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal
connections can set DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Repair as necessary.
Most DTCs set on start up but some must be set by driving the vehicle such that all
diagnostic monitors have run.
Note: Verify flash level of transmission controller. Some problems are
corrected by software upgrades to the transmission controller.
NOTE: Check for any Technical Service Bulletins that may apply.
Perform this procedure prior to Symptom diagnosis.All
Continue
Go To 2
74
TRANSMISSION - NAG1

Symptom:
IMPROPER RATIO
When Monitored and Set Condition:
IMPROPER RATIO
When Monitored: Engine rpm greater than 450 rpm, output speed greater than 180 rpm,
no N2 - N3 input speed sensor errors present, no gear selector lever errors present, no ABS
system errors, and all wheel speeds above 450 rpm.
Set Condition: No shifting operation and detected gear is not the actual gear No shifting
operation - detected (calculated) gear is less than actual(expected) gear or no plausible gear
is calculated or Actual turbine speed - calculated turbine speed > 300 rpm or calculated
transmission ratio is above threshold. During an Upshift - detected (calculated) gear is less
than actual(expected) gear-1. During Downshift - detected (calculated) gear is less than
actual (expected) gear
POSSIBLE CAUSES
TRANSMISSION MECHANICAL PROBLEM
TCM - IMPROPER RATIO
TEST ACTION APPLICABILITY
1NOTE: Low fluid level can be the cause of many transmission problems. If
the fluid level is low locate and repair the leak then check and adjust the
fluid level per the service information.
NOTE: Always perform diagnostics with a fully charged battery to avoid
false symptoms.
With the DRBIIIt, read the engine DTCs. Check and repair all engine DTCs prior to
performing transmission symptom diagnostics.
With the DRBIIIt, read and record all Transmission DTCs.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal
connections can set DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Repair as necessary.
Most DTCs set on start up but some must be set by driving the vehicle such that all
diagnostic monitors have run.
Note: Verify flash level of transmission controller. Some problems are
corrected by software upgrades to the transmission controller.
NOTE: Check for any Technical Service Bulletins that may apply.
Perform this procedure prior to Symptom diagnosis.All
Continue
Go To 2
76
TRANSMISSION - NAG1

Symptom:
INPUT SENSOR MISMATCH
When Monitored and Set Condition:
INPUT SENSOR MISMATCH
When Monitored: Engine speed greater than 450 rpm, no engine speed DTC's, no TCM
under-voltage system operation, no output speed sensor DTC's (signal from the ABS
system), all wheel speeds above 250 rpm (signal from the ABS system), no rear wheel speed
DTC's (signal from the ABS system), and no wheel slip detected (signal from the ABS
system), no shifting operation, N3 input speed sensor greater than 800 rpm and N2 input
speed sensor greater than 0 rpm and the TCM not in reset.
Set Condition: If the speed difference between the N2 and N3 input speed sensors is
greater than 150 rpm.
POSSIBLE CAUSES
SPEED SENSOR DTCS PRESENT
INTERMITTENT WIRING AND CONNECTORS
INTERNAL TRANSMISSION
TCM - INPUT SPEED SENSOR MISMATCH
TEST ACTION APPLICABILITY
1NOTE: Low fluid level can be the cause of many transmission problems. If
the fluid level is low locate and repair the leak then check and adjust the
fluid level per the service information.
NOTE: Always perform diagnostics with a fully charged battery to avoid
false symptoms.
With the DRBIIIt, read the engine DTCs. Check and repair all engine DTCs prior to
performing transmission symptom diagnostics.
With the DRBIIIt, read and record all Transmission DTCs.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal
connections can set DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Repair as necessary.
Most DTCs set on start up but some must be set by driving the vehicle such that all
diagnostic monitors have run.
Note: Verify flash level of transmission controller. Some problems are
corrected by software upgrades to the transmission controller.
NOTE: Check for any Technical Service Bulletins that may apply.
Perform this procedure prior to Symptom diagnosis.All
Continue
Go To 2
78
TRANSMISSION - NAG1

Symptom:
INPUT SENSOR OVERSPEED
When Monitored and Set Condition:
INPUT SENSOR OVERSPEED
When Monitored: Whenever the N2 input speed sensor is greater than 0 rpm
Set Condition: If the rpm of the N2 or N3 input speed sensor is greater than 7700 rpm
POSSIBLE CAUSES
INTERMITTENT WIRING AND CONNECTORS
INTERNAL TRANSMISSION
TCM - INPUT SENSOR OVERSPEED
TEST ACTION APPLICABILITY
1NOTE: Low fluid level can be the cause of many transmission problems. If
the fluid level is low locate and repair the leak then check and adjust the
fluid level per the service information.
NOTE: Always perform diagnostics with a fully charged battery to avoid
false symptoms.
With the DRBIIIt, read the engine DTCs. Check and repair all engine DTCs prior to
performing transmission symptom diagnostics.
With the DRBIIIt, read and record all Transmission DTCs.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal
connections can set DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Repair as necessary.
Most DTCs set on start up but some must be set by driving the vehicle such that all
diagnostic monitors have run.
Note: Verify flash level of transmission controller. Some problems are
corrected by software upgrades to the transmission controller.
NOTE: Check for any Technical Service Bulletins that may apply.
Perform this procedure prior to Symptom diagnosis.All
Continue
Go To 2
80
TRANSMISSION - NAG1

Symptom:
INVALID CONTROL MODULE VERSION
POSSIBLE CAUSES
TRANSMISSION CONTROL MODULE
INVALID CONTROL MODULE
TEST ACTION APPLICABILITY
1NOTE: Low fluid level can be the cause of many transmission problems. If
the fluid level is low locate and repair the leak then check and adjust the
fluid level per the service information.
NOTE: Always perform diagnostics with a fully charged battery to avoid
false symptoms.
With the DRBIIIt, read the engine DTCs. Check and repair all engine DTCs prior to
performing transmission symptom diagnostics.
With the DRBIIIt, read and record all Transmission DTCs.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal
connections can set DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Repair as necessary.
Most DTCs set on start up but some must be set by driving the vehicle such that all
diagnostic monitors have run.
Note: Verify flash level of transmission controller. Some problems are
corrected by software upgrades to the transmission controller.
NOTE: Check for any Technical Service Bulletins that may apply.
Perform this procedure prior to Symptom diagnosis.All
Continue
Go To 2
2 Validate if the TCM part number and flash is correct for the vehicle.
Is the TCM part number and flash correct for the vehicle?All
Ye s!Replace the Transmission Control Module per the Service Infor-
mation.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
No!Flash the controller is applicable. If the controller has the wrong
part number or cannot be flashed, replace the TCM per the
Service Information.
Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1.
83
TRANSMISSION - NAG1

Symptom:
MODULATING PRESSURE SOLENOID CIRCUIT
When Monitored and Set Condition:
MODULATING PRESSURE SOLENOID CIRCUIT
When Monitored: Always monitored with system active at each ignition cycle.
Set Condition: If the TCM detects a short to ground or battery on the solenoid control
circuit, shorted solenoid, open solenoid, or an open or shorted solenoid control circuit driver
in the TCM.
POSSIBLE CAUSES
INTERMITTENT WIRING AND CONNECTORS
MOD. PRESS SOLENOID CONTROL CIRCUIT OPEN
MOD. PRESS SOLENOID CONTROL CIRCUIT SHORT TO GROUND
MOD. PRESS SOLENOID CONTROL CIRCUIT SHORT TO OTHER CIRCUITS
MOD PRESS SOLENOID
TCM - MOD. PRESS SOLENOID CIRCUIT
TEST ACTION APPLICABILITY
1NOTE: Low fluid level can be the cause of many transmission problems. If
the fluid level is low locate and repair the leak then check and adjust the
fluid level per the service information.
NOTE: Always perform diagnostics with a fully charged battery to avoid
false symptoms.
With the DRBIIIt, read the engine DTCs. Check and repair all engine DTCs prior to
performing transmission symptom diagnostics.
With the DRBIIIt, read and record all Transmission DTCs.
NOTE: Check connectors - Clean/repair as necessary. Poor pin to terminal
connections can set DTCs.
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
Repair as necessary.
Most DTCs set on start up but some must be set by driving the vehicle such that all
diagnostic monitors have run.
Note: Verify flash level of transmission controller. Some problems are
corrected by software upgrades to the transmission controller.
NOTE: Check for any Technical Service Bulletins that may apply.
Perform this procedure prior to Symptom diagnosis.All
Continue
Go To 2
84
TRANSMISSION - NAG1