DTC P1261 Without RPO CTF
Circuit Description
The engine control module (ECM) supplies either 5 or 12 volts to power various sensors or switches. The power is supplied through resistances in the ECM which are so high in value that a test light will not light when connected to the circuit. In some cases, even an ordinary shop voltmeter will not give an accurate reading because the resistance is too low. The ECM controls output circuits such as the injectors, ISC, etc., by controlling the ground or the power feed circuit through transistors or through either of the following 2 devices:
| • | Output driver module (ODM) |
| • | Quad driver module (QDM) |
The input/output devices in the ECM include analog-to-digital converters, signal buffers, counters, and special drivers. The ECM controls most components with electronic switches which complete a ground circuit when turned ON. These switches are arranged in groups of 4 and 7, called either a surface-mounted quad driver module (QDM), which can independently control up to 4 output terminals, or QDMs which can independently control up to 7 outputs. Not all outputs are always used.
Conditions for Running the DTC
| • | Battery supply is more than 10 volts 2 seconds after resetting. |
| • | Engine is not cranking. |
Conditions for Setting the DTC
| • | CPU A/D conversion is not completed and CPU is functioning. |
| • | A sensed CPU internal error has occurred. |
| • | An A/D Conversion Error has occurred |
| • | The timer pulse time abnormal continues over 50 times. |
| • | Charging voltage abnormal and battery voltage higher than 10 volts, except on over speed. |
| • | Charging Circuit Error |
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | Clear the MIL and the DTC with a scan tool. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |
2 |
Did the DTC fail this ignition? | Go to Step 3 | Go to Intermittent Conditions |
3 | Inspect for radio wave interference. Ensure that there is not a wireless transmitter near the vehicle. Test for poor connections at the harness connectors or electronic noise due to harness GND floating Did you find and correct the condition? | Go to Step 7 | Go to Step 4 |
4 | Inspect the ECM grounds for a poor connection. Did you find and correct the condition? | Go to Step 6 | Go to Step 5 |
5 | Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data . Did you complete the replacement? | Go to Step 6 | -- |
6 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 7 |
7 | Does the scan tool display any DTCs that have not been diagnosed? | System OK | |
