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.
-
When Monitored:
Cold start condition. Ambient Air temperature between -7 degrees C and 50 degrees C (19.4 degrees F and 122 degrees F). Engine Coolant temperature between -7 degrees C
and 50 degrees C (19.4 degrees F and 122 degrees F).
The difference between the Ambient Air temp and ECT temp at Start is equal to or less than 10 degrees C (50 degrees F).
Engine running at idle only.
-
Set Condition:
Engine RPM is 50 RPM or more (depending on vehicle specifications), below idle speed for at least 3 seconds and the average spark advance is above the threshold, too much spark advance, for a specified
time limit. Two trip fault. Three good trips to turn off the MIL.
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
-
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
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
-
Remove the debris if possible or replace the Throttle Body Assembly. Disconnect the Battery when replacing the Throttle Body Assembly. After installation
is complete, use a scan tool and select the ETC RELEARN function.
-
Perform the POWERTRAIN VERIFICATION TEST.
(Refer to 9 - ENGINE - STANDARD PROCEDURE)
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
-
Drain the Fuel from the fuel tank into an approved gas holding tank and add clean fuel.
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
-
Replace the Throttle Body Assembly. Disconnect the Battery when replacing the Throttle Body Assembly. After installation is complete, use a scan tool and
select the ETC RELEARN function.
-
Perform the POWERTRAIN VERIFICATION TEST.
(Refer to 9 - ENGINE - STANDARD PROCEDURE)
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