P0203
P0203-FUEL INJECTOR 3 CIRCUITP0203 - Fuel Injector 3 Circuit:
Theory of Operation
The fueling strategy for NGC requires potentially three fuel pulses per cylinder per cycle. The first pulse is delivered starting at a programmed angle soon after the intake valve closes, for specified time duration. This is for two reasons, one to prevent any fuel from this pulse being delivered in the previous cycle and second to allow fueling to begin as early as possible in the current cycle. The second pulse is delivered for a specified time and is set to end at a programmed angle. The pulse must not extend past the end angle. There can be a separate value for each cylinder under the same operating conditions. This is done for two reasons, one to prevent any fuel from this pulse being delivered during the intake/exhaust valve overlap period, which tends to cause elevated emission levels. Also, allowing fuel to enter each cylinder at a slightly different angle tends to reduce any fuel pressure standing waves in the fuel rail. If the desired total fuel pulse-width increases, a third fuel pulse must be delivered. The third pulse, if necessary, is delivered for a specified time and must end at a programmed angle before the valve closes again. The third pulse in the cycle is controlled by its ending angle. This is also for two reasons, one to prevent any fuel from this pulse being delivered in the next cycle and second to allow fueling to end as late as possible in the current cycle. At high engine speeds, one or more of the pulses may be dropped from the fueling strategy.
WHEN MONITORED
With battery voltage greater than 10 volts. Auto Shutdown Relay energized. Engine speed less than 3000 rpm.
SET CONDITION
No inductive spike is detected after injector turn off.
POSSIBLE CAUSES
- (F42) ASD relay output circuit
- (K13) injector control No.3 circuit open
- (K13) injector control No.3 circuit shorted to ground
- Fuel injector
- PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview
Diagnostic Test
1. ACTIVE DTC
Ignition on, engine not running.
With a scan tool, read DTCs.
Q: Is the DTC active at this time?
YES: Go To 2
NO: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Component Tests and General Diagnostics
Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
2. (F42) ASD RELAY OUTPUT CIRCUIT
Turn the ignition off.
Disconnect the No.3 Fuel Injector harness connector.
Ignition on, engine not running.
With the scan tool, actuate the ASD Relay.
Using a 12-volt test light connected to ground, probe the (F42) ASD Relay Output circuit in the No.3 Fuel Injector harness connector.
Q: Does the test light illuminate brightly?
YES: Go To 3
NO: Repair the excessive resistance or short to ground in the (F42) ASD Relay Output circuit. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
3. FUEL INJECTOR
Using a 12-volt test light connected to 12-volts, probe the (K13) Injector Control No.3 circuit.
With the scan tool, actuate the No.3 Fuel Injector.
Q: What is the state of the test light during the actuation?
Brightly Blinking.
Replace the Fuel Injector. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
ON Constantly.
Go To 4
OFF Constantly.
Go To 5
4. (K13) INJECTOR CONTROL No.3 CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the C2 PCM harness connector.
Measure the resistance between ground and the (K13) Injector Control No.3 circuit in the Injector harness connector.
Q: Is the resistance below 100 Ohms?
YES: Repair the short to ground in the (K13) Injector Control No.3 circuit. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 6
5. (K13) INJECTOR CONTROL No.3 CIRCUIT OPEN
Turn the ignition off.
Disconnect the C2 PCM 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 to perform diagnosis.
Measure the resistance of the (K13) Injector Control No.3 circuit from the Fuel Injector harness connector to the appropriate terminal of special tool #8815.
Q: Is the resistance below 5.0 Ohms?
YES: Go To 6
NO: Repair the open in the (K13) Injector Control No.3 circuit. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
6. 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.
Q: Were there any problems found?
YES: Repair as necessary. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Replace and program the Powertrain Control Module. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test