For the Engine Data Line (EDL) Diagram, see Figure
“Engine Data Line Diagram”
.
Figure 1. Engine Data Line Diagram
Section 27.1.1
Circuit Functions
The ECM is programmed with two shift schedules — the Closed Throttle Mode and the Wide Open Throttle Mode.
- Closed Throttle Mode is for situations with moderate engine load. ECM pin 56 will be LOW (0 volts). This energizes the relay, turning off power to the solenoid, causing the transmission to shift at approximately 65% of the engine load.
- Wide Open Throttle Mode is for heavy load situations. The ECM pin 56 will be HIGH (12 volts). This de-energizes the relay causing 12 volts to be applied to the solenoid. In this mode, the ECM has shift schedules that occur at 80% of engine load.
When the engine is operating at less than the load shift point, ignition voltage is not applied to the shift solenoid. When the ECM commands a transmission shift, the relay coil ground is opened by the ECM, which de-energizes the relay, turning ON the power to the shift solenoid, causing it to shift.
Section 27.1.2
Fault Detection
The EST is used to initiate the KOEO Output Circuit Tests. This will test the enabling circuit between the key switch, through the relay coil and circuit to ECM pin 56. If an open or short (high or low) is found in this circuit, Flash Code 244 will be set.
Note that the test does not check relay function or the circuit to the shift solenoid. For transmission shift modulation wiring diagram, see Figure
“Transmission Shift Modulation — Wiring Diagram”
.
Figure 2. Transmission Shift Modulation — Wiring Diagram
Key ON engine OFF voltage checks at the EDL relay socket are listed in Table
“Voltage Checks at Engine Data Line Relay Socket”
.
| +Test Points− | Spec | Comments |
| 85 to Grd | 12v ± 1.5v | Should be power when key ON. If no power, check ground and power circuits from key switch; fuse F2. |
| 30 to Grd | 12v ± 1.5v | Should be power when key ON. If no power, check ground and power circuits from key switch; fuse F2. |
| 87A to 30 | > 10v | If no voltage present, open circuit or high resistance through shift solenoid, see OEM transmission information. |
| 86 to Grd | 0v | No voltage present when relay removed. |
Key ON engine OFF voltage checks at the ECM are listed in Table
“Voltage Checks at ECM”
.
| +Test Points− | Spec | Comments |
| +56 to −23 | 12v ± 1.5v | With EST tool enter OUTPUT STATE TEST set outputs HIGH (12v = shift modulator energized.) |
| +56 to −23 | 0v | With EST tool enter OUTPUT STATE TEST set outputs LOW (0v = shift modulator de-energized.) |
| If voltage states are correct the relay circuit is functioning correctly; if not, check relay, circuit from relay to ECM, or ECM programming. | ||
Circuit Resistance Checks are performed with the breakout box installed, the ECM power relay installed and the key to ON. Checks are listed in Table
“Circuit Resistance Checks”
.
| +Test Points− | Spec | Comments |
| 56 to 86 | < 5 Ω | Resistance from ECM to EDL relay. |
| 85 to 86 | 80 – 120 Ω | Measure resistance across relay coil. |
| 30 to 439K | < 5 Ω | Power from relay to fuse 439K. |
Fault Code Descriptions:
Fault Code 244 = High or low resistance detected in relay or relay coil during an Engine OFF test (Output Circuit Check).
Section 27.1.3
Extended Description
Engine Data Line (EDL) output from the ECM controls the Transmission Modulator Shift Solenoid Control Relay which in turn controls the Transmission Modulator Shift solenoid.
The ECM is programmed with two shift schedules: Closed Throttle Mode and Wide Open Throttle Mode. The Closed Throttle Mode schedule for a transmission is for situations with a moderate engine load. The transmission will shift at approximately 65 percent of engine load. The Wide Open Throttle Mode shift schedule has shift points that occur at 80 percent of engine load. This provides increased power in heavy load situations for passing or faster acceleration.
The ECM analyzes engine operating data and determines which mode is most appropriate for current operation. The physical Allison transmission uses EDL output from ECM connector pin 56 to select the most appropriate shift schedule depending upon engine loads.
When ECM pin 56 is LOW (0 volts), the transmission operates in the Closed Throttle Mode (normal shift schedule). When the ECM pin 56 is HIGH (12 volts), the transmission operates in the Wide Open Throttle Mode.
Section 27.1.4
Wide Open Throttle Mode Operation
In the Wide Open Throttle Mode, ECM pin 56 is HIGH (12 volts) and the XMSN Shift Modulator is energized. The Transmission Modulator Shift Solenoid Control Relay receives ignition power at common terminal 30 and control coil terminal 86. When ECM pin 56 is HIGH (12 volts), the relay does not energize. The ignition power on circuit 439K goes through the normally closed (N.C.) contacts (30 to 87A) to the Transmission Modulator Shift Solenoid, causing the shift solenoid to energize.
Section 27.1.5
Closed Throttle Mode Operation
In the closed Throttle Mode, ECM pin 56 is LOW (0 volts) and the Transmission Shift Modulator is not energized. When the ECM pin 56 is LOW (0 volts), circuit 150C grounds the Modulator Shift Control Relay control coil causing the relay to energize, opening the normally closed (N.C.) contacts (30 to 87A) in relay, turning OFF the power to the Transmission Modulator Shift Solenoid, which is de-energized.
Section 27.1.6
ECM Diagnostics
The ECM does not continuously monitor the EDL circuits. To check these circuits, use the ProLink EST to perform the KOEO — Output Circuit Checks (OCC).
Section 27.1.7
Flash Code 244
ATA Code SID 248 FMI 11
ECM: EDL OCC Fault
The OCC Test checks the relay control coil circuits and the relay control coil for opens or shorts (high or low). If a defect is noted, Flash Code 244 will be set. The Engine Warning light does not turn ON.
Note that the ECM diagnostics do not check the actual operation of the Modulator Shift Solenoid Control relay or the Modulator Shift Solenoid. For these reasons, it is possible for the Allison AT/MT transmission Modulator Shift Solenoid not to function, without a fault code.
| Series 40E Troubleshooting Manual – 6SE241 |
| Generated on 10-13-2008 |