Mechanics

CHEVROLET S-10 FUEL INJECTOR PROBLEM

1998 Chevrolet S-10 • 17,599 miles

Wont start code P0200
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January 18, 2013.




CIRCUIT DESCRIPTION

The Powertrain Control Module (PCM) has four injector driver circuits, each of which controls an injector. The PCM monitors the current in each driver circuit by measuring a voltage drop through a fixed resistor and is able to control the driver circuit. The current through each driver can rise to a peak of 4 amps to quickly open the injectors and can reduce to 1 amp to hold the injectors open. This is called peak and hold. If the current cannot reach a 4 amp peak, a DTC is set. This DTC is also set if an injector driver is shorted to voltage.

CONDITIONS FOR SETTING THE DTC

Injector current is less than 4 amps.
Battery voltage is more than 9 volts.
Above conditions met for 7 seconds.

ACTION TAKEN WHEN THE DTC SETS

The Malfunction Indicator Lamp (MIL) illuminates.
The PCM records the operating conditions at the time when the diagnostic fails. This information stores in the Freeze Frame and Failure Records buffers.
A history DTC stores.
The coolant fan turns ON.

CONDITIONS FOR CLEARING THE MIL/DTC

The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault.
A history DTC will clear after 40 consecutive warm up cycles without a fault.
The MIL/DTC(s) can be cleared by using the scan tool.

DIAGNOSTIC AIDS

An injector driver circuit that is open or shorted to voltage will cause a DTC P0200 to set and will also cause a misfire due to an inoperative injector. A misfire DTC should also be set indicating which cylinder is inoperative.

Long term and short term fuel trims that are excessively high or low are a good indication that an injector is malfunctioning. Use Fuel Injector Balance Test [Sequential Fuel Injection (SFI) ] to check for malfunctioning injectors.

TEST DESCRIPTION

Number(s) below refer to the step number(s) on the Diagnostic Table.

The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.

This step determines if DTC P0200 is the result of a hard malfunction or an intermittent condition.

This step test the harness wiring and for PCM control of the fuel injectors using the test light J 34780-2. If the test light blinks, the PCM and wiring to the fuel injectors are OK. Fuel Injector Balance Test (SFI) will check if the fuel injectors are malfunctioning.
Whether the test light was ON steady or OFF while cranking the engine narrows the possible malfunctions down to just a few.
Because the test light was ON steady, voltage to the fuel injector is OK, but the fuel injector driver circuit is grounded at all times. This step determines if the circuitry is shorted to ground or the PCM is malfunctioning.

Replacement PCMs must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline information for PCM reprogramming and also refer to the Crankshaft Position (CKP) System Variation Learn Procedure for the Crankshaft Position System Variation Procedure.
Determines if voltage is available to the fuel injector. Voltage is supplied through the fuel pump relay so the engine must be cranked to see voltage at the fuel injector.
This step determines if the fuel injector driver circuit is open, shorted to voltage or if the PCM is malfunctioning.
Since the voltage is supplied to the fuel injector on a single circuit before the injector harness, the malfunction could only be a poor connection or open in the injector harness. An open before the harness would result in a Cranks But Does Not Run complaint.
Check the fuel injector electrical connector, the fuel injector harness connector and the PCM for poor connections or corroded terminals.

This is the flow chart

Roy

ASEMaster6371
Jan 18, 2013.


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