Engine Controls - System/component Tests: Diagnosis

Electronic Ignition Timing Inspection (1.8L)

Start and warm engine to normal operating temperature. Turn off all accessories. Install scan tool. Using scan tool, monitor engine RPM parameter. With transaxle in Neutral, ensure idle speed is 650-750 RPM. Turn ignition switchto LOCK position. Connect timing light to spark plug wire No. 1.
Connect timing light according to manufacturer's instructions. Connect a fused jumper wire between terminals E1 and TE1 of Data Link Connector (DLC) in engine compartment. see scheme 4 Start engine and aim timing light at timing mark. Notch on crankshaft pulley should align at 8-10 degrees BTDC on timing indicator at each flash of timing light.

Evaporation Emission (EVAP) Canister Purge Valve Diagnosis (1.0L & 1.3L)

Disconnect EVAP canister purge valve electrical connector. Measure resistance between EVAP canister purge valve terminals. Resistance should be 28-39 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, replace EVAP canister purge valve.
Disconnect EVAP canister purge valve vacuum hoses from intake manifold and EVAP canister. Blow into EVAP canister purge valve vacuum hose that was disconnected from EVAP canister. Air should not pass through EVAP canister purge valve and exit from intake manifold hose. (Scheme 2)or (Scheme 3).
Apply battery voltage and ground to EVAP canister purge valve terminals. With EVAP canister purge valve energized, blow into EVAP canister purge valve vacuum hose that was disconnected from EVAP canister. Air should pass through EVAP canister purge valve and exit from intake manifold hose. If operation is not as specified, replace EVAP canister purge valve.

Scheme 1

Scheme 2

Evaporation Emission (EVAP) Canister Purge Valve Diagnosis (1.8L)

Remove EVAP canister. Install a plug into port No. 5. (Scheme 4) While holding port No. 2 closed, blow into port No. 1. Air should pass from port No. 4. While holding ports No. 2 and No. 4 closed, blow into port No. 1. Air should NOT pass from port No. 3.
Connect a hand-held vacuum/pressure pump to port No. 2. Apply 1.01 in. Hg vacuum. Plug port No. 3 and check that vacuum does NOT decrease. Unplug port No. 3 and check that vacuum does decrease.
Remove hand-held vacuum/pressure pump from port No. 2 and connect to port No. 1. Apply 1.01 in. Hg vacuum. Plug port No. 3 and check that air flows into port No. 2. If operation is not as specified, replace EVAP canister purge valve.

Scheme 3

Evaporation Emission (EVAP) Canister Purge Solenoid Valve Diagnosis (1.8L)

Remove EVAP canister purge solenoid valve. Measure resistance between EVAP canister purge solenoid valve terminals. Resistance should be 27-33 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, replace EVAP canister purge solenoid valve.
Check for continuity between each EVAP canister purge solenoid valve terminal and valve body. If continuity exists, go to next step. If continuity does not exist, replace EVAP canister purge solenoid valve.
Blow into EVAP canister purge solenoid valve port No. 1. (Scheme 5) Air should pass through port No. 2 with a high amount of resistance. Apply battery voltage and ground to EVAP canister purge solenoid valve terminals. With EVAP canister purge solenoid valve energized, blow into EVAP canister purge solenoid valve port No. 1. Air should pass easily through port No. 2. If operation is not as specified, replace EVAP canister purge solenoid valve.

Scheme 4

Evaporation Emission (EVAP) Canister Vent Solenoid Diagnosis (1.0L & 1.3L)

Disconnect EVAP canister vent solenoid electrical connector. Measure resistance between EVAP canister vent solenoid terminals. Resistance should be 25-30 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, replace EVAP canister vent solenoid.
Disconnect EVAP canister vent solenoid hose from EVAP canister. Blow into EVAP canister vent solenoid hose that was disconnected from EVAP canister. Air should pass through EVAP canister vent solenoid. (Scheme 2)or (Scheme 3).
Apply battery voltage and ground to EVAP canister vent solenoid terminals. With EVAP canister vent solenoid energized, blow into EVAP canister vent solenoid hose that was disconnected from EVAP canister. Air should NOT pass through EVAP canister vent solenoid and exit from other end. If operation is not as specified, replace EVAP canister vent solenoid.

EVAP Fuel Tank Pressure Control Solenoid Vacuum Valve Diagnosis (1.0L & 1.3L)

Disconnect EVAP fuel tank pressure control solenoid vacuum valve electrical connector. Measure resistance between EVAP fuel tank pressure control solenoid vacuum valve terminals. Resistance should be 28-36 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, replace EVAP fuel tank pressure control solenoid vacuum valve.
Disconnect EVAP fuel tank pressure control solenoid vacuum valve vacuum hoses from intake manifold and vacuum pipe from EVAP fuel tank pressure control solenoid vacuum valve. Blow into EVAP fuel tank pressure control solenoid vacuum valve vacuum hose that was disconnected from vacuum pipe. Air should NOT pass through EVAP fuel tank pressure control solenoid vacuum valve and exit from intake manifold hose. (Scheme 2)or (Scheme 3).
Apply battery voltage and ground to EVAP fuel tank pressure control solenoid vacuum valve terminals. With EVAP fuel tank pressure control solenoid vacuum valve energized, blow into EVAP fuel tank pressure control solenoid vacuum valve vacuum hose that was disconnected from vacuum pipe. Air should pass through EVAP fuel tank pressure control solenoid vacuum valve and exit from intake manifold hose. If operation is not as specified, replace EVAP fuel tank pressure control solenoid vacuum valve.

Evaporative Emission (EVAP) Fuel Tank Pressure Vent Solenoid Valve Diagnosis (1.8L)

Remove EVAP fuel tank pressure vent solenoid valve. Measure resistance between EVAP fuel tank pressure vent solenoid valve terminals. Resistance should be 37-44 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, replace EVAP fuel tank pressure vent solenoid valve.
Check for continuity between each EVAP fuel tank pressure vent solenoid valve terminal and valve body. If continuity exists, go to next step. If continuity does not exist, replace EVAP fuel tank pressure vent solenoid valve.
Blow into EVAP fuel tank pressure vent solenoid valve port No. 1. see scheme 12 Air should pass through port No. 2. Apply battery voltage and ground to EVAP fuel tank pressure vent solenoid valve terminals. With EVAP fuel tank pressure vent solenoid valve energized, blow into EVAP fuel tank pressure vent solenoid valve port No. 1. Air should pass through valve and exit from port No. 3. If operation is not as specified, replace EVAP fuel tank pressure vent solenoid valve.

Scheme 5

Fuel Tank Pressure Sensor Diagnosis (1.0L & 1.3L)

A malfunction in fuel tank pressure sensor circuit can set Diagnostic Trouble Codes (DTCs) P0450 and P0451. For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article.

Fuel Tank Pressure Sensor Diagnosis (1.8L)

Disconnect fuel tank pressure sensor electrical connector. Turn ignition on with engine off. Using a DVOM, measure voltage between fuel tank pressure sensor harness connector 5-volt reference circuit and ground circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, diagnose problem using DTC P0450 test procedure. See appropriate SELF-DIAGNOSTICS article.
Using a DVOM, measure voltage between ground and fuel tank pressure sensor harness connector input circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, diagnose problem using DTC P0450 test procedure. See appropriate SELF-DIAGNOSTICS article.
Turn ignition off. Reconnect fuel tank pressure sensor electrical connector. Disconnect vacuum hose from fuel tank pressure sensor. Connect a hand-held vacuum/pressure pump to fuel tank pressure sensor. Set DVOM to DC scale. Using DVOM, backprobe fuel tank pressure sensor 5-volt reference circuit and ground circuit of PCM. See appropriate wiring diagram in WIRING DIAGRAMS article. Measure voltage while applying and releasing vacuum as follows: Apply .59 in. Hg vacuum to fuel tank pressure sensor. Voltage should be 1.3-2.1 volts. Release vacuum from fuel tank pressure sensor. Voltage should be 3.0-3.6 volts. Apply .22 psi (.015 kg/cm 2 ) pressure to fuel tank pressure sensor. Voltage should be 4.2-4.8 volts.

If voltage readings are as specified, fuel tank pressure sensor is okay. If any voltage reading is not as specified, replace fuel tank pressure sensor.

Fuel Tank Pressure Control Valve Diagnosis (1.0L)

Note. Fuel tank pressure control valve will not allow air to flow from fuel tank port to canister port until tank port side pressure is more than .5 psi (.035 kg/cm 2 ).

Remove fuel tank pressure control valve. (Scheme 2) Connect a hose to port marked TANK on fuel tank pressure control valve. Blow forcefully into hose. Air should pass through valve and exit from port marked CAN on fuel tank pressure control valve.
Remove hose from TANK port. Connect hose to port marked CAN on fuel tank pressure control valve. Blow softly into hose. Air should pass through valve and exit from port marked TANK on fuel tank pressure control valve.
Apply vacuum to fuel tank pressure control valve vacuum port. With vacuum applied, blow into port marked TANK. Air should pass through valve and exit from port marked CAN on fuel tank pressure control valve. If operation is not as specified, replace fuel tank pressure control valve.

Fuel Tank Pressure Control Valve Diagnosis (1.3L)

Remove fuel tank pressure control valve. (Scheme 3) Connect a hose to fuel tank side port (Black) on fuel tank pressure control valve. Blow forcefully into hose. Air should pass through valve and exit from canister side port (Orange) on fuel tank pressure control valve.
Remove hose from fuel tank side port (Black). Connect hose to canister side port (Orange) on fuel tank pressure control valve. Blow softly into hose. Air should pass through valve and exit from fuel tank side port (Black) on fuel tank pressure control valve. If operation is not as specified, replace fuel tank pressure control valve.

Early Fuel Evaporation (EFE) Heater Diagnosis (1.0L)

Note. Early Fuel Evaporation (EFE) heater may also be referred to as Positive Temperature Coefficient (PTC) heater.

A malfunction in EFE heater circuit can set Diagnostic Trouble Code (DTC) P1250. For test procedure with DTC set, see appropriate SELF-DIAGNOSTICS article.

Circuit Description

When A/C compressor clutch is in operation, A/C compressor control module will send an A/C idle-up signal to PCM. PCM signals Idle Speed Control (ISC) motor which activates a plunger to open throttle plate. When throttle plate opens, engine idle speed increases, preventing rough idle or stalling.

Diagnostic Aids

An intermittent condition may be caused by a poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections before component replacement.

Diagnosis & Repair

Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
Install scan tool. Start and warm engine to normal operating temperature. Turn off all accessories. Using scan tool, monitor A/C parameter while turning A/C switch on and blower speed switch to any position except off. If scan tool indicates on with A/C operating, system is functioning normally. If scan tool does not indicate on with A/C operating, go to next step.
Start engine. Turn A/C on (A/C operating). Using a voltmeter connected to ground, backprobe PCM connector A/C idle-up signal circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If voltage is zero volts, go to next step. If voltage is not zero volts, go to step 6 .
Start engine. Turn A/C off. Using a voltmeter connected to ground, backprobe PCM connector A/C idle-up signal circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If battery voltage is present, go to step 7 . If battery voltage is not present, go to next step.
Turn ignition off. Disconnect PCM electrical connector C3. Back out A/C idle-up signal wire from PCM electrical connector. Reconnect PCM electrical connector C3. Turn ignition on with engine off. Using a voltmeter connected to ground, backprobe through PCM connector to PCM A/C idle-up signal circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, go to step 12 .
Check for an open in A/C idle-up signal circuit between PCM and A/C compressor control module. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 11 .
Start engine. Turn A/C off. Using a voltmeter connected to ground, backprobe PCM connector A/C cut-out signal circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If voltage is zero volts, go to next step. If voltage is not zero volts, go to step 12 .
Start engine. Turn A/C on (A/C operating). Using a voltmeter connected to ground, backprobe PCM connector A/C cut-out signal circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If battery voltage is present, go to «DIAGNOSTIC AIDS»(ref-181-S42512372262000030800000) . If battery voltage is not present, go to next step.
Check for an open in A/C cut-out signal circuit between PCM and A/C compressor control module. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to next step.
Disconnect A/C compressor control module electrical connector. Turn ignition on with engine off. Using a voltmeter, measure voltage at A/C compressor control module A/C cut-out signal circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If battery voltage is present, go to step 12 . If battery voltage is not present, go to next step.
Replace A/C compressor control module. After repairs, go to step 13 .
Replace PCM. After repairs, go to next step.
After repairs are completed, operate vehicle within conditions under which original symptom was observed. If system operates properly, repair is complete. If system does not operate properly, go to «DIAGNOSTIC AIDS»(ref-181-S42512372262000030800000) .

Powertrain Control Module (PCM) receives an idle-up signal from diode module. This signal is present whenever one or more of the following systems is turned on or operated

Headlights or parking lights.
Rear window defogger.
Heater blower motor.

Idle Speed Control (ISC) motor will increase throttle valve opening and engine RPM will slightly increase to compensate for additional electrical load.

A short to ground in electrical load idle-up signal circuit between diode module and PCM may cause an open TAIL fuse. An intermittent condition may be caused by a poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Note. Before proceeding with this test, ensure rear defogger, parking lights and blower motor all operate properly.

Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
Install scan tool. Start and warm engine to normal operating temperature. Turn off all accessories. Using scan tool, monitor electrical load parameter while turning parking lights, rear window defogger, and blower motor on and off. If scan tool does not indicate on when accessories are turned on and off when accessories are turned off, go to next step. If scan tool indicates accessories on and off as specified, system is functioning normally.
If engine RPM does not increase when at least one accessory is turned on, go to next step. If engine RPM does increase, go to step 7 .
Turn ignition off. Disconnect PCM electrical connectors. Turn ignition on with engine off. Using a test light connected to ground, probe PCM connector electrical load idle-up signal circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Turn headlight switch to Park or Head position. If test light illuminates, go to next step. If test light does not illuminate, go to step 6 .
Check for poor terminal connections at PCM. Repair as necessary. After repairs, go to step 10 . If connections are okay, go to step 9 .
Check for an open in electrical load idle-up signal circuit between diode module and PCM. Repair as necessary. After repairs, go to step 10 . If circuit is okay, go to step 8 .
Check components and circuits in related systems which did not increase engine RPM: Faulty blower motor speed selector switch, poor connection or an open in blower motor speed selector switch circuit to diode module. Faulty headlight switch, poor connection or an open in headlight switch circuit to diode module. Faulty rear defogger switch, poor connection or an open in rear defogger switch circuit to diode module. Repair as necessary. After repairs, go to step 10 . If no repairs were necessary, go to next step
Replace diode module. After repairs, go to step 10 .
Replace PCM. After repairs, go to next step.
After repairs are completed, operate vehicle within conditions under which original symptom was observed. If system operates properly, repair is complete. If system does not operate properly, go to «DIAGNOSTIC AIDS»(ref-181-S03700089962000030800000) .

Powertrain Control Module (PCM) receives an idle-up signal from taillight relay and rear defogger relay. This signal is present whenever one or more of the following systems is turned on or operated

Headlights or parking lights.
Rear window defogger.

Using scan tool, monitor electrical load parameter. When rear defogger and/or headlights are turned on, scan tool should indicate on. When rear defogger and/or headlights are turned off, scan tool should indicate off.

An intermittent condition may be caused by a poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Note. Before proceeding with this test, ensure rear defogger and parking lights operate properly.

Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
Install scan tool. Start and warm engine to normal operating temperature. Turn off all accessories. Using scan tool, monitor electrical load parameter while turning rear window defogger on and off. If engine RPM does not increase when switch is turned on, go to step 5 . If engine RPM does increase, go to next step.
Using scan tool, monitor electrical load parameter while turning parking lights on and off. If engine RPM does not increase when switch is turned on, go to step 7 . If engine RPM does increase, system is functioning normally.
Turn ignition on with engine off. Using a test light connected to ground, backprobe electrical load idle-up signal circuit at PCM connector C3 terminal No. 2. Turn rear defogger switch to ON position. If test light illuminates, go to step 8 . If test light does not illuminate, go to next step.
Turn ignition off. Disconnect PCM electrical connectors. Check for an open or short in electrical load idle-up signal circuit between rear defogger switch and PCM. Repair as necessary. After repairs, go to step 10 . If circuit is okay, go to step 9 .
Turn ignition on with engine off. Using a test light connected to ground, backprobe electrical load idle-up signal circuit at PCM connector C3 terminal No. 13. Turn parking light switch on. If test light illuminates, go to step 8 . If test light does not illuminate, go to next step.
Turn ignition off. Disconnect PCM electrical connectors. Check for an open or short in electrical load idle-up signal circuit between parking light switch and PCM. Repair as necessary. After repairs, go to step 10 . If circuit is okay, go to next step.
Check for a short to ground in diagnostic request circuit between underhood data link connector and PCM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 10 . If circuit is okay, go to next step.
Replace PCM. After repairs, go to next step.
After repairs are completed, operate vehicle within conditions under which original symptom was observed. If system operates properly, repair is complete. If system does not operate properly, go to «DIAGNOSTIC AIDS»(ref-181-S09618277532000030800000) .

PCM energizes fuel injector when reference pulses are received from ignition system. Fuel pump pressurizes fuel injector as long as engine is cranking and PCM is receiving ignition system reference pulses.

Check for faulty fuel injector. Check for partially blocked fuel injector nozzle. Check fuel injector resistance. Resistance should be 0.5-1.5 ohms at 68°F (20°C). Resistance of fuel injector resistor should be 1.9-2.1 ohms at 68°F (20°C).

Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
Turn ignition off. Disconnect fuel injector electrical connector. Install Fuel Injector Test Light (J-34730-2B) on fuel injector harness connector. Crank engine and observe test light. If test light flashes while cranking engine, go to next step. If test light does not flash, go to step 5 .
Measure resistance of fuel injector (fuel injector side). Resistance should be 0.5-1.5 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, go to step 10 .
Check for fuel restriction or for a partially blocked fuel injector nozzle. Repair as necessary. After repairs, go to step 17 . If no restriction is present, check fuel system electrical circuit. See FUEL SYSTEM ELECTRICAL CIRCUIT test under appropriate NO START - ENGINE CRANKS OKAY under NO START DIAGNOSIS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
If test light remains illuminated while cranking engine, go to next step. If test light does not remain illuminated, go to step 7 .
Check for short to ground in fuel injector control circuit between PCM and fuel injector. Repair as necessary. After repairs, go to step 17 . If circuit is okay, go to step 12 .
Remove test light from fuel injector harness connector. Turn ignition on with engine off. Using a voltmeter, measure voltage between ground and fuel injector connector (harness side) ignition feed circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, go to step 13 .
Connect test light between battery voltage and fuel injector connector (harness side) fuel injector control circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Crank engine and observe test light. If test light flashes while cranking engine, go to next step. If test light does not flash, go to step 11 .
Check for poor connection at fuel injector harness connector. Repair as necessary. After repairs, go to step 17 . If connection is okay, go to next step.
Replace fuel injector. After repairs, go to step 17 .
Check for an open in fuel injector control circuit. Repair as necessary. After repairs, go to step 17 . If circuit is okay, go to next step.
Replace PCM. After repairs, go to step 17 .
Turn ignition on with engine off. Using a voltmeter connected to ground, backprobe fuel injector resistor connector ignition feed circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, go to step 15 .
Check for an open or short to ground in fuel injector ignition feed circuit between fuel injector and fuel injector resistor. Repair as necessary. After repairs, go to step 17 . If circuit is okay, go to step 16 .
Repair open in ignition feed circuit between fuel injector resistor and main relay. After repairs, go to step 17 .
Replace fuel injector resistor. After repairs, go to next step.
After repairs are completed, operate vehicle within conditions under which original symptom was observed. If system operates properly, repair is complete. If system does not operate properly, go to «DIAGNOSTIC AIDS»(ref-181-S27151929242000030800000) .

PCM energizes fuel injectors sequentially when reference pulses are received from ignition system. Fuel pump pressurizes fuel injectors as long as engine is cranking and PCM is receiving ignition system reference pulses.

Check for contaminated fuel, water or poor quality fuel causing a no-start condition. Check for faulty fuel injector spray pattern. Using scan tool, check engine coolant temperature sensor. A faulty sensor can cause PCM to not deliver proper amounts of fuel to injectors. Check fuel injector resistance. Resistance should be 0.5-1.5 ohms at 68°F (20°C).

Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
Turn ignition off. Disconnect all 4 fuel injector electrical connectors. Install Fuel Injector Test Light (J-34730-2B) on each fuel injector harness connector. Crank engine and observe test light for each injector. If test light flashes for each injector while cranking engine, go to next step. If test light does not flash for each injector, go to step 5 .
Using ohmmeter, measure resistance of each fuel injector (fuel injector side). If resistance is 0.5-1.5 ohms at 68°F (20°C), go to next step. If resistance is not 0.5-1.5 ohms at 68°F (20°C), go to step 10 .
Check for fuel restrictions or for a partly blocked fuel injector nozzle. Repair as necessary. After repairs go to step 17 . If no fuel restriction was found or fuel injector nozzle is okay, check fuel system electrical circuit. See FUEL SYSTEM ELECTRICAL CIRCUIT test under appropriate NO START - ENGINE CRANKS OKAY under NO START DIAGNOSIS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
If test light remains illuminated on any injector while cranking engine, go to next step. If test light does not remain illuminated on any injector, go to step 7 .
Check for an short to ground in fuel injector control circuit between fuel injector and PCM. Repair as necessary. After repairs, go to step 17 . If circuit is okay, go to step 12 .
Remove test light from fuel injector harness connector. Turn ignition on with engine off. Using a voltmeter, measure voltage between ground and fuel injector connector (harness side) ignition feed circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, go to step 13 .
Connect test light between battery voltage and fuel injector connector (harness side) fuel injector control circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Crank engine and observe test light. If test light flashes while cranking engine, go to next step. If test light does not flash, go to step 11 .
Check for poor connection at fuel injector harness connector. Repair as necessary. After repairs, go to step 17 . If connection is okay, go to next step.
Replace fuel injector. After repairs, go to step 17 .
Check for an open in fuel injector control circuit. Repair as necessary. After repairs, go to step 17 . If circuit is okay, go to next step.
Replace PCM. After repairs, go to step 17 .
Turn ignition on with engine off. Using voltmeter connected to ground, backprobe fuel injector resistor connector (harness side) ignition feed circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, go to step 15 .
Check for an open or short to ground in ignition feed circuit between fuel injector and fuel injector resistor. Repair as necessary. After repairs, go to step 17 . If circuit is okay, go to step 16 .
Repair open in ignition feed circuit between fuel injector resistor and main relay. After repairs, go to step 17 .
Replace fuel injector resistor. After repairs, go to next step.
After repairs are completed, operate vehicle within conditions under which original symptom was observed. If system operates properly, repair is complete. If system does not operate properly, go to «DIAGNOSTIC AIDS»(ref-181-S40616314412000030800000) .

Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
Turn ignition off. Disconnect all 4 fuel injector electrical connectors. Install Fuel Injector Test Light (J-34730-2B) on each fuel injector harness connector. Crank engine and observe test light for each injector. If test light flashes for each injector while cranking engine, perform fuel injector coil test. See «FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE BETWEEN 50-95°F (1.8L)»(ref-181-S17881697642000030800000) . If test light does not flash for each injector, go to next step.
If test light flashes for at least one injector while cranking engine, go to step 5 . If test light does not flash for at least one injector, go to next step.
Check for an open in fuel injector ignition feed circuit between ignition switch and fuel injector. Also, check for an open in ground circuit at ground connection G106. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 12 .
If test light remains illuminated on any injector while cranking engine, go to next step. If test light does not remain illuminated on any injector, go to step 8 .
Turn ignition off. Install Fuel Injector Test Light (J-34730-2B) on fuel injector harness connector of fuel injector circuit that test light remains illuminated. Disconnect PCM harness connector C1. Turn ignition on with engine on. If test light illuminates, go to next step. If test light does not illuminate, go to step 11 .
Repair short to ground in faulty fuel injector control circuit between fuel injector and PCM. After repairs, go to step 12 .
Remove fuel injector test light from fuel injector harness connector. Connect a test light between ground and fuel injector ignition feed circuit of fuel injector harness connector that did not flash. Turn ignition on with engine off. If test light illuminates, go to step 10 . If test light does not illuminate, go to next step.
Repair open in fuel injector ignition feed circuit between fuel injector and junction block No. 2. After repairs, go to step 12 .
Check for an open in faulty fuel injector control circuit between fuel injector and PCM. Repair as necessary. Repeat steps 5 - 10) until fuel injector test light flashes on all 4 injector circuits. After repairs, go to step 12 . If fuel injector control circuit is okay, go to next step.
Replace PCM. After repairs, go to next step.
Using scan tool, clear Diagnostic Trouble Codes (DTCs). After repairs are completed, operate vehicle within conditions under which original symptom was observed. If system operates properly, repair is complete. If system does not operate properly, go to «DIAGNOSTIC AIDS»(ref-181-S22144132542000030800000) .

Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
Install scan tool. Using scan tool, check engine coolant temperature. If engine coolant temperature is within range of 50-95°F (10-35°C), go to next step. If engine coolant temperature is not within range of 50-95°F (10-35°C), go to «FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE NOT WITHIN RANGE OF 50-95°F (1.8L)»(ref-181-S41399865302000030800000) .
Turn ignition off. Relieve fuel pressure. Access fuel injector connectors as required. Install Fuel Injector Tester (J-39021) to positive battery voltage and ground. Set amperage supply selector switch on tester to COIL TEST 0.5 AMP position. Connect DVOM to fuel injector tester. Set DVOM to tenths scale (0.0). Install fuel injector tester on fuel injector. Press PUSH TO START TEST button on tester. Observe voltage reading on DVOM. Record lowest voltage reading observed after first second of test. Repeat for each fuel injector. If any fuel injector has an erratic voltage reading, or voltage reading is not with range of 6.7-7.7 volts, go to next step. If voltage reading is within range of 6.7-7.7 volts, go to «FUEL INJECTOR BALANCE TEST (1.8L)»(ref-181-S25840211532000030800000) .
Replace faulty fuel injector(s). After replacing fuel injector, go to «FUEL INJECTOR BALANCE TEST (1.8L)»(ref-181-S25840211532000030800000) .

Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
Install scan tool. Using scan tool, check engine coolant temperature. If engine coolant temperature is within range of 50-95°F (10-35°C), go to «FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE BETWEEN 50-95°F (1.8L)»(ref-181-S17881697642000030800000) . If engine coolant temperature is not within range of 50-95°F (10-35°C), go to next step.
Turn ignition off. Relieve fuel pressure. Access fuel injector connectors as required. Install Fuel Injector Tester (J-39021) to positive battery voltage and ground. Set amperage supply selector switch on tester to COIL TEST 0.5 AMP position. Connect DVOM to fuel injector tester. Set DVOM to tenths scale (0.0). Install fuel injector tester on fuel injector. Press PUSH TO START TEST button on tester. Observe voltage reading on DVOM. Record lowest voltage reading observed after first second of test. Repeat for each fuel injector. Note highest voltage reading recorded except for reading greater than 9.5 volts. Subtract lowest voltage reading from highest voltage reading. Perform this calculation for all injectors. If any value from calculation is greater than one volt, go to next step. If no value from calculation is greater than one volt, go to «FUEL INJECTOR BALANCE TEST (1.8L)»(ref-181-S25840211532000030800000) .
Replace faulty fuel injector(s). Injector is faulty if the subtracted value is greater than 0.6 volt, the initial voltage reading is greater than 9.5 volts, or voltage reading is erratic. After replacing fuel injector, go to «FUEL INJECTOR BALANCE TEST (1.8L)»(ref-181-S25840211532000030800000) .

Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
Perform fuel injector coil test. See «FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE BETWEEN 50-95°F (1.8L)»(ref-181-S17881697642000030800000) . After performing fuel injector coil test, go to next step.
If engine coolant temperature is greater than 201°F (94°C), go to next step. If engine coolant temperature is less than 201°F (94°C), go to step 5 .
Allow engine to cool to less than 201°F (94°C). After engine coolant temperature is less than 201°F (94°C), go to next step.
Install Fuel Pressure Gauge (J-34730-1A). Using scan tool, energize fuel pump. Place fuel pressure gauge bleed hose into a container and bleed out air. Observe fuel pressure gauge. If fuel pressure is 44-50 psi (3.0-3.4 kg/cm 2 ), go to next step. If fuel pressure is not 44-50 psi (3.0-3.4 kg/cm 2 ), go to FUEL SYSTEM PRESSURE TEST under BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
Turn fuel pump off. If fuel pressure remains constant, go to next step. If fuel pressure does not remain constant, go to FUEL SYSTEM PRESSURE TEST under BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
Access fuel injector connectors as required. Install Fuel Injector Tester (J-39021) to positive battery voltage and ground. Set amperage supply selector switch on tester to BALANCE TEST 0.5-2.5 AMP position. Install fuel injector tester on fuel injector. Using scan tool, energize fuel pump. Record fuel pressure after pressure stabilizes. This is the first reading. Press PUSH TO START TEST button on tester to energize injector. Record fuel pressure after needle stops moving. This is the second reading. Repeat steps 1 - 6) for each fuel injector. Subtract second pressure reading from first pressure reading. Resulting value is pressure drop value. Perform this calculation for all injectors. Add all pressure drop values together to obtain total pressure drop value. Divide total drop pressure by number of injectors to obtain average pressure drop value. If any injector pressure drop value is 1.5 psi (1.0 kg/cm 2 ) greater than or less than average pressure drop value, go to next step. If any injector pressure drop value is not 1.5 psi (1.0 kg/cm 2 ) greater than or less than average pressure drop value, go to appropriate TROUBLE SHOOTING - NO CODES article.
Operate engine to prevent flooding. Repeat step 7 for injectors that are not as specified. If any injector pressure drop value is still 1.5 psi (1.0 kg/cm 2 ) greater than or less than average pressure drop value, go to next step. If any injector pressure drop value is not 1.5 psi (1.0 kg/cm 2 ) greater than or less than average pressure drop value, go to appropriate TROUBLE SHOOTING - NO CODES article.
Replace faulty fuel injector(s). After replacing fuel injector, system is okay.

UPSHIFT indicator light is controlled by PCM and illuminates when preferred transaxle shift point for maximum fuel economy is reached.

Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
Turn ignition on with engine off. If UPSHIFT indicator light is illuminated, go to next step. If UPSHIFT indicator light is not illuminated, go to step 6 .
Start engine. If UPSHIFT indicator light goes out, go to «DIAGNOSTIC AIDS»(ref-181-S02688599552000030800000) . If UPSHIFT indicator light remains illuminated, go to next step.
Check for a short to ground in UPSHIFT indicator light control circuit between instrument cluster and PCM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to next step.
Check for a short to ground in instrument panel printed circuit board. Repair as necessary. After repairs, go to step 11 . If circuit board is okay, go to step 10 .
Turn ignition off. Disconnect PCM electrical connectors. Connect a fused jumper wire between PCM harness connector UPSHIFT indicator light control circuit and ground. See appropriate wiring diagram in WIRING DIAGRAMS article. Turn ignition on with engine off. If UPSHIFT indicator light is illuminated, go to step 10 . If UPSHIFT indicator light is not illuminated, go to next step.
Remove jumper wire. Using fused jumper wire, backprobe instrument panel cluster assembly connector C3 UPSHIFT indicator light control circuit to ground. See appropriate wiring diagram in WIRING DIAGRAMS article. If UPSHIFT indicator light is illuminated, go to next step. If UPSHIFT indicator light is not illuminated, go to step 9 .
Check for an open in UPSHIFT indicator light control circuit between instrument cluster and PCM. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to step 10 .
Check for an open IGN fuse, faulty UPSHIFT indicator light bulb, an open in ignition feed circuit to instrument cluster, a poor connection at instrument cluster, or an open in instrument panel printed circuit board. Repair as necessary. After repairs, go to step 11 . If no problem is found, go to «DIAGNOSTIC AIDS»(ref-181-S02688599552000030800000) .
Replace PCM. After repairs, go to next step.
After repairs are completed, operate vehicle within conditions under which original symptom was observed. If system operates properly, repair is complete. If system does not operate properly, go to «DIAGNOSTIC AIDS»(ref-181-S02688599552000030800000) .

Engine Controls - System/component Tests: Diagnosis Chevrolet Prizm I