P050D

P050D-COLD START ROUGH IDLE







Theory of Operation

Spark adjustment during a cold start is intended to provide quick response to idle speed variations. The Powertrain Control Module (PCM) monitors spark advance on a cold start over a period of time, then compares the average spark advance to a threshold.

- When Monitored:
During a cold start condition, with the difference between the ambient air temperature (AAT) and engine coolant temperature (ECT) at startup below 10° C, and the engine running at idle.

- Set Condition:
The Powertrain Control Module (PCM) detects that engine speed is 50 RPM or more (depending on vehicle specifications) below target idle speed for more than three seconds, and the average spark advance is above the failure threshold for more than the specified limit. Two trip fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DIAGNOSTIC TROUBLE CODE (DTC)

NOTE: Low battery voltage can cause excessive current draw in very hot and very cold ambient temperatures. Look closely at the temperatures at which this DTC set and make sure the battery can pass a load test before continuing.

NOTE: Diagnose and repair any other DTCs set in the PCM before proceeding with this test.

1. Turn the ignition on.
2. Using the scan tool, select View DTCs and review the DTC environmental information.

Is the good trip counter greater than 0?

Yes

- The DTC is not active at this time. Perform the CHECKING FOR AN INTERMITTENT DTC diagnostic procedure. Checking for an Intermittent DTC.

No

- Go To 2

2. THROTTLE PLATE INSPECTION
1. Turn the ignition off.
2. Remove the air cleaner assembly.
3. Check for any signs of a foreign material (ice, dirt, or excessive carbon build up) on the throttle plate or in the bore causing the throttle plate to stick.

Were any problems found?

Yes

- Remove the debris or obstruction.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Go To 3

3. RESTRICTED INTAKE AIR SYSTEM
1. Inspect the intake air system for any blockage or restrictions such as a collapsed air intake duct or clogged air filter.

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Go To 4

4. CONTAMINATED FUEL
1. Inspect the fuel for contamination (dirt, water, or other foreign material).

Were any problems found?

Yes

- Drain the fuel from the fuel tank into an approved gas holding tank and add clean fuel. Procedures.

No

- Go To 5

5. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Throttle Body and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test. PCM Verification Test.

No

- Replace the Powertrain Control Module (PCM).
- Perform the PCM Verification Test. PCM Verification Test.