Chrysler 300/300 Touring/300C, Dodge Magnum. Manual — part 2026

P1790-FAULT IMMEDIATELY AFTER SHIFT

For a complete wiring diagram Refer to Section 8W.

•

When Monitored:
After a Gear Ratio Error code is stored.

•

Set Condition:
After a Gear Ratio Error DTC has already been set. The DTC is set if the fault happened within 1.3 seconds
of a shift. The DTC set time will vary from 1.214 seconds to 15 seconds.

Possible Causes

FAULT AFTER SHIFT

Always perform the 42RLE Pre-Diagnostic Troubleshooting Procedure before proceeding. (Refer to 21 -
TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

Theory of Operation

This DTC is not stored alone. It is stored if a Gear Ratio DTC is detected immediately after shift. The existence of
DTC P1790 indicates a mechanical or hydraulic (not electrical) related problems. It should be noted, however, that
all mechanical problems don’t necessarily result in DTC P1790. When this DTC exists, diagnosing the system
should be based on the associated DTC and only mechanical causes should be considered.

Diagnostic Test

1.

FAULT AFTER SHIFT

This DTC is set along with a Gear Ratio DTC. Perform the appropriate test for the Gear Ratio DTC stored.

NOTE: Check Pending DTCs or 1 trip failures if there are no Active or Stored Gear Ratio DTCs.

View repair.

Repair

Refer to the Transmission category and perform the appropriate diagnostic procedure.

Perform 42RLE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

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P1794-SPEED SENSOR GROUND ERROR

For a complete wiring diagram Refer to Section 8W.

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•

When Monitored:
Every 7ms after a controler reset with transmission range in neutral.

•

Set Condition:
After a PCM reset in neutral and Input/Output Ratio equals a ratio of 2.50 to 1.0 ± 50.0 RPM.

Possible Causes

SPEED SENSOR GROUND CIRCUIT OPEN

POWERTRAIN CONTROL MODULE

Always perform the 42RLE Pre-Diagnostic Troubleshooting Procedure before proceeding. (Refer to 21 -
TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

Theory of Operation

The two speed sensors in the transmission system and use a common ground circuit. The loss of this common
ground results in the input signal being sensed by both sensors. After a reset and in neutral, and observing a certain
Output/Input ratio will increment the Speed Check Fault Counter. Because the speed sensors and the thermistor
share the same ground wire, this DTC may indicate a loss of the common speed sensor ground. In some cases this
fault will cause a Gear Ratio Error DTC to be set.

Diagnostic Test

1.

PCM AND WIRING

Turn the ignition off to the lock position.

Remove the Starter Relay.

CAUTION: Removal of the Starter Relay is to prevent a Transmission, NO RESPONSE, condition and disable
the starter.
Install the Transmission Simulator, Miller tool #8333 and the Electronic Transmission Adapter kit 8333-1A.

Ignition on, engine not running.

With the Transmission Simulator, set the

9

Input/Output Speed

9

switch to

9

ON

9

and the rotary switch to the

9

3000/

1250

9

position.

With the scan tool, monitor the Input and Output Speed Sensor readings.

Does the Input Speed read 3000 RPM and the Output Speed read 1250 RPM, ± 50 RPM?

Yes

>> Go To 2

No

>> Go To 3

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2.

(T13) SPEED SENSOR GROUND CIRCUIT OPEN

Turn the ignition off to the lock position.

Disconnect the PCM C4 harness connector.

Disconnect the Input and Output Speed Sensor harness connectors.

NOTE: Check connectors - Clean/repair as necessary.

CAUTION: Do not probe the PCM harness connectors. Probing the
PCM harness connectors will damage the PCM terminals resulting
in poor terminal to pin connection. Install Miller Special Tool #8815
to perform diagnosis.
Measure the resistance of the (T13) Speed Sensor Ground circuit from
the appropriate terminal of special tool #8815 to the Input and Output
Speed Sensor harness connectors.

Is the resistance above 5.0 ohms on either circuit?

Yes

>> Repair the (T13) Speed Sensor Ground circuit for an open.

Perform 42RLE TRANSMISSION VERIFICATION TEST -
VER 1. (Refer to 21 - TRANSMISSION/TRANSAXLE/AU-
TOMATIC - 42RLE - STANDARD PROCEDURE)

No

>> Using the schematics as a guide, check the Powertrain

Control Module (PCM) terminals for corrosion, damage, or
terminal push out. Pay particular attention to all power and
ground circuits. If no problems are found, replace the PCM
per the Service Information. With the scan tool PERFORM
QUICK LEARN, then program Pinion Factor in the Front
Control Module. (Refer to 8 - ELECTRICAL/ELECTRONIC
CONTROL MODULES/POWERTRAIN CONTROL MOD-
ULE - REMOVAL)

Perform 42RLE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

3.

INTERMITTENT WIRING AND CONNECTORS

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

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

Wiggle the wires while checking for shorted and open circuits.

With the scan tool, check the EATX DTC EVENT DATA to help identify the conditions in which the DTC was set.

Were there any problems found?

Yes

>> Repair as necessary.

Perform 42RLE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

No

>> Test Complete.

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