Circuit Description
The throttle body assembly contains an idle speed control (ISC) motor that is used to control the engine speed at idle. The engine control module (ECM) commands the ISC motor to adjust the throttle angle for idle speed control. An idle switch is also integrated into the throttle body assembly. The idle switch position is dependant upon the position of the throttle. The ECM uses a high and low control circuit to command the ISC motor. If the ECM detects a fault with the ISC motor control circuits or motor, this DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1511 Idle Speed Control (ISC) Motor Control Circuit
Conditions for Running the DTC
| • | The engine is running. |
| • | The ignition 1 voltage is more than 10 volts. |
| • | The ISC motor angle is between 0.5-21 degrees. |
| • | This DTC runs continuously once the above conditions are met. |
Conditions for Setting the DTC
| • | The ECM detects that the commanded duty cycle is more than 45 percent for 6 seconds. |
| OR |
| • | The ECM detects that the commanded duty cycle is less than -42 percent for 6 seconds. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
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. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connect End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | |||||||
2 |
Is DTC P0122, P0123, P0222 or P0223 also set? | -- | Go to Step 3 | |||||||
3 |
Does the ISC motor position sensor parameter change when the throttle is open? | -- | Go to Step 4 | Go to Step 5 | ||||||
4 |
Did the DTC fail this ignition? | -- | Go to Step 5 | Go to Intermittent Conditions | ||||||
5 |
Is the voltage more than the specified value? | 11 V | Go to Step 6 | Go to Step 9 | ||||||
6 | Measure the low control circuit of the ISC motor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems. Is the voltage more than the specified value? | 11 V | Go to Step 7 | Go to Step 10 | ||||||
7 | While Measuring the voltage at the high control circuit of the ISC motor, toggle the idle switch circuit to a good ground with a 3-amp fused jumper wire. Does the voltage value change when the jumper is installed? | -- | Go to Step 8 | Go to Step 11 | ||||||
8 | While Measuring the voltage at the low control circuit of the ISC motor, toggle the idle switch circuit to a good ground with a 3-amp fused jumper wire. Does the voltage value change when the jumper is installed? | -- | Go to Step 13 | Go to Step 12 | ||||||
9 | Test the high control circuit of the ISC motor for the following:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16 | ||||||
10 | Test the low control circuit of the ISC motor for the following:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16 | ||||||
11 | Test the high control circuit of the ISC motor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16 | ||||||
12 |
Important: The engine control module (ECM) may be damaged if the circuit is shorted to battery positive voltage. Test the low control circuit of the ISC motor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16 | ||||||
13 | Test the high control circuit of the ISC motor for a high resistance or a short to the low control circuit of the ISC motor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 14 | ||||||
14 | Test the low control circuit of the ISC motor for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 15 | ||||||
15 | Test for shorted terminals and for poor connections at the throttle body assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 17 | ||||||
16 | Test for shorted terminals and for poor connections at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18 | ||||||
17 | Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement . Did you complete the replacement? | -- | Go to Step 19 | -- | ||||||
18 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 19 | -- | ||||||
19 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 20 | ||||||
20 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
