Chrysler 300/300 Touring/300C, Dodge Magnum. Manual — part 1897

Theory of Operation

The NAG1 transmission has two input speed sensors 1 and 2 (N2 and N3), both speed sensors are located on the
valve body. The speed sensors are hall effect speed sensors that are used by the Transmission Control Module
(TCM) to calculate the transmissions input speed. Since the input speed could not be measured directly, two of the
drive elements are measured. Two input speed sensors were required because both drive elements are not active
in all gears.

The input speed sensors 1 and 2 will report the same input speed in gears 2nd, 3rd or 4th. If the 1 and 2 input
speed sensor signals are not the same in these gears, the TCM will set the DTC P2784-Input Speed Sensor 1/2
Correlation. The input speed sensor 2 is not reported in 1st and 5th gears. The input speed sensor 1 (N2) is not
reported in Reverse. The P01704-Input Speed Sensor 1 Overspeed and P01705-Input Speed Sensor 2 Overspeed
DTCs are rationality checks designed to detect a major transmission failure. If either DTC is detected, the TCM will
place the transmission in Neutral.

•

When Monitored:
Continuously with the ignition on, engine running, transmission in gear, and Input Speed Sensor 2 (N3) greater
than 0 RPM

•

Set Condition:
If the RPM of the Input Speed Sensor 2 (N3) is greater than 7700 RPM.

Possible Causes

INTERNAL TRANSMISSION

TRANSMISSION CONTROL MODULE

Always perform the NAG1 Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 -
TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)

Diagnostic Test

1.

CHECK TO SEE IF DTC IS CURRENT

Turn the ignition on.

With the scan tool, erase Transmission DTCs.

Raise the vehicle on the hoist.

Start the engine.

With the scan tool, monitor the Input Speed Sensor 2 RPM.

Firmly apply the brakes and place the gear selector in Drive.

WARNING: To avoid personal injury or death, keep hands and feet clear of rotating wheels.
Release the brakes and raise the engine RPM to allow the transmission to upshift to the 2-3 and 3-4 shift schedule.

Did the Input Speed Sensor 2 display an RPM above 7700?

Yes

>> Go To 2

No

>> Go To 3

2.

INTERNAL TRANSMISSION

This DTC is an indication of a internal transmission failure.

Remove the Transmission Oil Pan and inspect for excessive debris such as clutch friction material or metal con-
tamination.

Is there any indication of an internal transmission failure?

Yes

>> Repair internal transmission as necessary per the Service Information. (Refer to 21 - TRANSMISSION/

TRANSAXLE/AUTOMATIC - NAG1 - REMOVAL)

Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)

No

>> Using the schematics as a guide, check the Transmission Control Module (TCM) terminals for corrosion,

damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems

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are found, replace the TCM per the Service Information. (Refer to 8 - ELECTRICAL/ELECTRONIC
CONTROL MODULES/TRANSMISSION CONTROL MODULE - DESCRIPTION)

Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)

3.

INTERMITTENT WIRING AND CONNECTORS

The conditions necessary to set this DTC are not present at this time.

Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.

Wiggle the wiring and connectors while checking for any possible open or shorted circuits.

Check for any Service Information Tune-ups or Technical Service Bulletins that may apply.

Were there any problems found?

Yes

>> Repair as necessary.

Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)

No

>> Test Complete.

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AUTOMATIC TRANSMISSION NAG1 - ELECTRICAL DIAGNOSTICS

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P1731-INCORRECT GEAR ENGAGED

For a complete wiring diagram Refer to Section 8W

Theory of Operation

The TCM compares the calculated gear with the gear the transmission has actually engaged. The actual gear is
identified by verifying the signals of the two input speed sensors 1 (N2) and 2 (N3) as well as the transmission
output speed (from the ABS system). 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 points. 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.

•

When Monitored:
The conditions for gear detection are: engine speed greater than 450 rpm, no input speed sensor failures are
active, no selector lever error active, selector lever is not in intermediate position, selector lever position is not
showing power-up value, no output speed error is active, no transfer case error is active, output speed (ABS
system) greater than 180 rpm, no wheel speed (ABS system) overspeed detected.

•

Set Condition:
The detected gear calculated by the TCM is not identical to the actual gear. Exception: detected gear is 1st
and actual gear is 2nd. If the problem is present for three consecutive ignition cycles, the TCM places the
transmission into Limp-in mode until the DTC is cleared by the scan tool.

Possible Causes

TRANSMISSION SOLENOID DTCS PRESENT

ABS DTCS PRESENT

INTERNAL TRANSMISSION

TRANSMISSION CONTROL MODULE

Always perform the NAG1 Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 -
TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)

Diagnostic Test

1.

CHECK IF TRANSMISSION SOLENOID DTCS ARE PRESENT

With the scan tool, check for other transmission DTCs.

Are there any Transmission Solenoid DTCS present?

Yes

>> Refer to the Transmission category and perform the appropriate symptom(s). (Refer to 21 - TRANS-

MISSION/TRANSAXLE/AUTOMATIC - NAG1 - DIAGNOSIS AND TESTING)

No

>> Go To 2

2.

CHECK IF ABS DTCS ARE PRESENT

With the scan tool, check for ABS DTCs.

Are there any ABS DTCs present?

Yes

>> Refer to 5 - BRAKES - ABS ELECTRICAL DIAGNOSTICS category and perform the appropriate symp-

tom.

Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)

No

>> Go To 3

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3.

CHECK FOR INTERNAL TRANSMISSION PROBLEM

This DTC is usually set due to an internal transmission problem such as but not limited to: stuck solenoid valve
and/or contamination in the valve body, broken springs, leaking clutch seals, dislodged or broken snap ring.

Inspect internal transmission. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - NAG1 - DIAGNOSIS
AND TESTING)

Were there any problems found?

Yes

>> Repair internal transmission as necessary per the Service Information. (Refer to 21 - TRANSMISSION/

TRANSAXLE/AUTOMATIC - NAG1 - REMOVAL)

Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)

No

>> Using the schematics as a guide, check the Transmission Control Module (TCM) terminals for corrosion,

damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems
are found, replace the TCM per the Service Information. (Refer to 8 - ELECTRICAL/ELECTRONIC
CONTROL MODULES/TRANSMISSION CONTROL MODULE - DESCRIPTION)

Perform NAG1 TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - NAG1 - STANDARD PROCEDURE)

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