P0726-ENGINE SPEED INPUT CIRCUIT RANGE/PERFORMANCE

For a complete wiring diagram Refer to Section 8W.

Theory of Operation

The Transmission Control System calculates the engine rpm by directly reading the engine crank position sensor. It compares the calculated value to the engine speed sensor signal transmitted from the Engine Control System over the controllers internal BUS. The calculated engine rpm is also compared to a minimum and a maximum value. Note: Due to the integration of the Powertrain Control Module (PCM) and Transmission Control Module (TCM), BUS communication between the modules is internal and unserviceable.

When Monitored:
Continuously every 7 msec with the ignition on and engine running.
Set Condition:
This DTC will set when the calculated engine speed is less than 390 rpm with the engine running, or greater than 8000 rpm, for the period of 2.0 seconds. The PCM will place the Transmission in Limp-in when this DTC is set. Note: This is not a Transmission Input Speed Sensor DTC.

Possible Causes

RELATED ENGINE DTCS PRESENT

CRANK POSITION SENSOR OR WIRING

POWERTRAIN CONTROL MODULE

Always perform the 45RFE/545RFE Pre-Diagnostic Troubleshooting Procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Diagnostic Test

1. CHECK FOR RELATED ENGINE DTCS

NOTE: This is not a Transmission Input Speed Sensor DTC.

Ignition on, engine not running.
With the scan tool, read all Engine DTCs. This includes any active or stored or one trip DTCs.

Are there any engine rpm related DTCs present?

Yes

Refer to the Powertrain category and perform the appropriate symptom.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

No

Go To 2

2. CHECK IF DTC IS CURRENT

Ignition on, engine not running.
With a scan tool, read and record all DTC EVENT DATA.
With the scan tool, erase all active and stored transmission DTCs. (Note: it may be necessary to perform a battery disconnect with the scan tool to clear DTC EVENT DATA.)
Using the DTC EVENT DATA, duplicate the conditions in which the original DTC set.
With the scan tool, read transmission and engine DTCs.

NOTE: Refer to all engine DTCs first in the following question.

Pick the answer below that best describes your findings, (this includes one trip failures).

Transmission DTC P0726 set

Using the schematics as a guide, check the Powertrain Control Module (PCM) terminals for corrosion, damage, or terminal push out. Also check the Crank Position sensor and wiring. 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.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

Engine DTC set

Refer to the Driveability category and perform the appropriate symptom.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

No DTC set at all

Go To 3

3. CHECK 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 wires while checking for shorted and open circuits.
With the scan tool, check the DTC EVENT DATA to help identify the conditions in which the DTC was set.

Were there any problems found?

Yes

Repair as necessary.

Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

No

Test Complete.