P050B-COLD START IGNITION TIMING PERFORMANCE





For a complete wiring diagram Refer to Section 8W.

Theory of Operation


Spark adjustment during a cold start is intended to provide quick response to idle speed variations. The spark adjust diagnostics monitors spark advance on a cold start over a period of time, then compares the average spark advance to a threshold.


Possible Causes
RESTRICTED INTAKE AIR SYSTEM
LOW BATTERY VOLTAGE
FUEL CONTAMINATION
EXCESSIVE RESISTANCE IN THE (K124) ETC MOTOR (+) CIRCUIT
EXCESSIVE RESISTANCE IN THE (K126) ETC MOTOR (-) CIRCUIT
ETC MOTOR/THROTTLE BODY
PCM


Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).



Diagnostic Test

1. ACTIVE DTC

Ignition on, engine not running.

NOTE: Low battery voltage can also cause excessive current draw, in very hot and very cold ambient temperatures. Make sure the battery can pass a load test before continuing.


With a scan tool, select View DTCs.
Diagnose any other PCM DTCs before continuing.
Start the engine.
Allow the engine to reach normal operating temperature.
With a scan tool, select View DTCs.

NOTE: It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.



Is the DTC Active or Pending at this time?

Yes


No

2. THROTTLE PLATE INSPECTION

Turn the ignition off.
Remove the Air Cleaner Assembly from the Throttle Body.
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 signs of foreign material or scoring of the throttle plate or bore found?

Yes


No

3. DIRTY AIR FILTER

Remove and inspect the Air Filter.

Is the Air Filter dirty?

Yes


No

4. CONTAMINATED FUEL

Inspect the Fuel for contamination. (Dirt, water, or other foreign material)

Is the fuel contaminated?

Yes


No

5. EXCESSIVE RESISTANCE IN THE (K124) ETC MOTOR (+) CIRCUIT

Turn the ignition off.
Disconnect the C2 harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 along with the #8815-1 to perform the diagnosis.


Using a voltmeter perform a voltage drop test. Backprobe the (K124) ETC Motor (+) circuit at the Throttle Body harness connector and probe the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.


Start the engine and allow it to reach normal operating temperature.
Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes


No

6. EXCESSIVE RESISTANCE IN THE (K126) ETC MOTOR (-) CIRCUIT

Turn the ignition off.
Move the voltmeter leads to backprobe the (K126) ETC Motor (-) circuit at the Throttle Body harness connector and to probe the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.


Start the engine and allow it to reach normal operating temperature.
Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes


No

7. ETC MOTOR



Turn the ignition off.

NOTE: Take the following measurement using special tool #8815 to avoid possible damage to the Throttle Body harness connector.


Connect the Throttle Body harness connector.
Disconnect special tool #8815-1 from the C2 PCM harness connector.
Measure the resistance of the ETC Motor by probing the appropriate terminals of special tool #8815 for the (K124) ETC Positive circuit and the (K126) ETC Negative circuit.

Is the resistance between 2.5 and 25 ohms at closed throttle?

Yes


No

8. PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.


Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

Were there any problems found?

Yes


No