For the self test input switch function diagram, see Figure
“Self Test Input Switch Function Diagram”
.
Figure 1. Self Test Input Switch Function Diagram
Section 41.1.1
Self Test Input Switch
The Self Test Input (STI) switch runs the Key On Engine OFF (KOEO) Standard Tests. (STI is sometimes referred to as the EST.) Faults detected during the test result in active fault codes that are transmitted as flash codes with the warning light. If no faults are detected, the ECM will flash Code 111, indicating no faults detected.
ECM pin 34 has 12 volts with the key ON and engine OFF. Depressing the STI switch grounds pin 34, causes it to change from 12 volts to 0 volts, signaling the ECM to start the KOEO Standard Tests.
Section 41.1.2
Engine Warning Light WARN
When the key switch is turned to ON, the amber Engine Warning Light turns ON and stays ON. The ECM runs normal start-up tests and then turns OFF. If the ECM detects a problem, the WARN remains ON.
Ignition power is applied to the WARN lamp. The ground side of the WARN lamp is connected to ECM pin 55, a ground switch. The ECM applies 5 volts to pin 55 (light OFF) or 0 volts (light ON), in response to engine conditions.
Section 41.1.3
Fault Detection Management
The ECM can detect an open WARN lamp circuit during a Standard Engine OFF Test during which an output circuit test is automatically performed. There are no ECM diagnostics for the STI circuits.
For the self test input switch, see Figure
“Self Test Input Switch “
.
Figure 2. Self Test Input Switch
The STI switch is tested with the ignition key OFF. Checks are listed in Table
“Self Test Input Switch Test”
.
| Test Points | Spec | Comments |
| Across Switch Terminals | > 1,000 Ω open position | Less than 1,000 Ω, replace the switch. |
| Across Switch Terminals | < 5 Ω closed position | Greater than 5 Ω, replace the switch. |
The STI switch connection is tested with the ignition key OFF. Checks are listed in Table
“Self Test Input Switch Connection Test, Key OFF”
.
| Test Points | Spec | Comments |
| 98 to Grd | > 1,000 Ω open position | Less than 1,000 Ω, locate short to ground. |
The STI switch connection is tested with the ignition key ON. Checks are listed in Table
“Self Test Input Switch Connection Test, Key ON”
.
| Test Points | Spec | Comments |
| 98 to Grd | 5 ± .5 volts | Less than 4.5v, check connections; if 0 volts, check for open/short to ground in circuit 98. |
| 98 to 98 – Grd | 5 ± .5 volts | Less than 4.5v, check connections; if 0 volts, check for open in ground circuit. |
Section 41.1.3.1
Key ON, No Warning Light
If the warning light does not turn on when the key is turned ON:
- Check the fuse and bulb condition.
- Disconnect 379 from the ECM and install the breakout box to harness; jumper terminal 17 to ground; note if light is ON.
- If the light is ON, the ECM is defective.
- If the light does not turn ON, check the circuit for an open condition.
- If the light goes OFF, the ECM is defective.
Section 41.1.3.2
Warning Light STAYS ON
If the warning light stays ON after the self test:
- Check for active fault conditions (use EST or STI flash codes).
- If active fault conditions are present, correct the faults.
- If no fault conditions are present, go to the next step.
- Disconnect 379 from the ECM and note if light stays ON.
- If light stays ON, check for short to ground in circuit.
Section 41.1.3.3
Fault Code Descriptions
Fault Code 266 = Output Circuit Check detected during the Standard Test; indicates high or low resistance in Warn Lamp circuit.
Section 41.1.4
STI Switch
The STI switch (or EST) can be used to run the KOEO Standard Tests. Faults detected during this test result in active fault codes that are transmitted as flash codes with the Warning Light. If no faults are detected, the ECM will flash Code 111, indicating no faults detected.
Depressing the STI switch with the key ON and engine OFF starts the test cycle. KOEO Standard Tests include the ECM Internal Tests and the Output Circuit Check (OCC) tests.
The normally open switch has one pole connected through circuit 98 and the ECM connector 379 to the ECM STI pin 34. The other switch pole is connected (circuit 98–G/11–GA) to the G2 ground stud.
The ECM pin 34 has 5 volts with the key ON and the engine OFF. Depressing the STI switch grounds pin 34, causing it to change from 5 volts to 0 volts, signaling the ECM to start the KOEO Standard Tests.
Section 41.1.5
Engine Warning Light WARN
When the key switch is turned to ON, the amber Engine Warning Light turns ON and stays ON, while the ECM runs normal start-up tests, and then turns OFF. If the ECM detects a problem, the WARN remains ON.
Ignition power WARN is applied to the Engine Warning Light. The ground side of the WARN is connected to ECM pin 55, which is a ground switch. The ECM applies 12 volts to terminal 17 (light OFF) or 0 volts (light ON), in response to engine conditions.
Section 41.1.6
ECM Diagnostics
There are no ECM diagnostics for the STI or Warning Light circuits.
Section 41.1.7
Before Troubleshooting
Before troubleshooting, ensure that the batteries are fully charged. Check the battery connections and grounds for clean, tight connections free of damage. Voltage tests will give misleading results if the batteries are not fully charged.
Before troubleshooting, inspect circuit connectors for pushed back, loose, or damaged (spread or bent) terminals, or wires with cut strands, etc. Wires and connections must be free of damage or corrosion. When some connectors corrode, a light white residue will be present and must be removed.
Before troubleshooting, inspect the suspect circuit grounds for clean, tight connections, free of damage.
| Series 40E Troubleshooting Manual – 6SE241 |
| Generated on 10-13-2008 |