5.0l/5.7l Vins [f,8] Pfi "a" Charts Chevrolet Camaro III рестайлинг

MODEL IDENTIFICATION

Note. The following conditions must be met before testing: Engine at operating temperature, Engine in closed loop operation, Engine idling ("Engine Run" column), Test terminal NOT grounded, and Scanner or ALDL tool NOT installed.

Repair procedures in this article are sometimes identified by a specific body code. The following table lists GM division, model name, and body types that apply to the body codes.

MODEL IDENTIFICATION

DESCRIPTION

The computerized engine control system monitors as many as 19 engine/vehicle functions. (Scheme 242) This system controls engine operation and lowers exhaust emissions while maintaining fuel economy and driveability. The Electronic Control Module (ECM) is the "brain" of the CCC system.

The computerized engine control system is primarily an emission control system, designed to maintain a 14.7:1 air/fuel ratio under all operating conditions. When the ideal air/fuel ratio is maintained, the 3-way catalytic converter can control Oxides of Nitrogen (NOx), Hydrocarbon (HC) and Carbon Monoxide (CO) emissions.

ECM Conditions Sensed & Systems Controlled. Scheme 242

DIAGNOSTIC SYSTEM OPERATION

The ECM of computerized engine control system is equipped with a self-diagnostic system which detects system failures or abnormalities. As a bulb and system check, "SERVICE ENGINE SOON" light will glow when ignition switch is turned to "ON" position and engine is not running. When engine is started, light should go out. If not, a malfunction has been detected in the computerized engine control system or "SERVICE ENGINE SOON" light circuit is faulty.

When a malfunction occurs, ECM will illuminate the "SERVICE ENGINE SOON" light located on instrument panel. When malfunction is detected and light is turned on, a corresponding trouble code will be stored in ECM memory. Malfunctions are recorded as "hard failures" or as "intermittent failures".

"HARD FAILURES"

Hard failures cause "SERVICE ENGINE SOON" light to glow and remain on until the malfunction is repaired. If light comes on and remains on during vehicle operation, cause of malfunction must be determined using diagnostic charts. If a sensor fails, ECM will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is driveable, but loss of good driveability will most likely be encountered.

"INTERMITTENT FAILURES"

Intermittent failures cause "SERVICE ENGINE SOON" light to flicker or illuminate and go out about 10 seconds after the intermittent fault goes away. The corresponding trouble code, however, will be retained in ECM memory. If related fault does not reoccur within 50 engine restarts, related trouble code will be erased from ECM memory. Intermittent failures may be caused by sensor, connector or wiring related problems. See INTERMITTENTS in the CEC TESTS W/O CODES article in this section.

Note. Trouble codes will be recorded at various operating times. Some codes require operation of that sensor or switch for 5 seconds. Others may require operation for 5 minutes or longer under engine load. For more information on testing with codes, refer to the CEC PFI TESTS/CODES article in this section.

BASIC DIAGNOSTIC PROCEDURE

Note. Most computerized engine control problems are the result of mechanical breakdowns, poor electrical connections or damaged vacuum hoses. Before considering the computer system as a possible cause of problems, ignition high tension wires, fuel supply, electrical connections and vacuum hoses should be checked. Failure to do so may result in lost diagnostic time.

Diagnosis of the computerized engine control system should be performed in the following order

1. Make sure that all engine systems not related to the computer system are operating properly. Do not proceed with testing unless all other problems have been repaired.
2. Perform appropriate DIAGNOSTIC CIRCUIT CHECK for that system. If trouble codes were displayed (other than Code 12), decide whether codes are "hard" or "intermittent" trouble codes. "Hard" codes will cause the "SERVICE ENGINE SOON" light to illuminate continuously while engine is running. See ECM TROUBLE CODE DEFINITIONS table in the CEC PFI TESTS/CODES article in this section.
3. If no trouble codes were displayed, perform FIELD SERVICE MODE CHECK procedures.
4. If no trouble is indicated by the FIELD SERVICE MODE check and/or a driveability problem exists, refer to SYMPTOM DIAGNOSIS TROUBLE SHOOTING procedures in the CEC TESTS W/O CODES article in this section or SCAN TESTER USAGE and SCAN TESTER - TEST DATA PARAMATERS in this article. The comments there will send you to the proper component charts or tell you the most likely system/component to check.
5. After any repairs are made, clear any trouble codes and perform FIELD SERVICE MODE check again.

Scheme 243

1. Turn ignition on. Do not start engine. "SERVICE ENGINE SOON" light should glow. Locate Assembly Line Data Link (ALDL) connector attached to ECM wiring harness under instrument panel, left or right of steering column (under cigar lighter plate in center console on Fiero). Insert jumper wire across terminal "B", "DIAGNOSTIC TERMINAL" and terminal "A", "GROUND". (Scheme 243) CAUTION: Inserting spade lug (jumper lead) into terminals of ALDL connector grounds "DIAGNOSTIC TERMINAL". Do not ground ALDL connector until after ignition is on (engine not running). (Scheme 243): ALDL Connector Terminal Identification NOTE: In some of the diagnostic and trouble shooting charts the Assembly Line Data Link (ALDL) may also be referred to as the Assembly Line Communication Link (ALCL). These are referring to the same connector. It is also the test point for connection of aftermarket "Scan" testers.
2. "SERVICE ENGINE SOON" light should flash Code "12". Code "12" consists of "FLASH", pause, "FLASH", "FLASH" followed by a longer pause. Trouble Code "12" will be repeated 2 more times. If any other trouble codes are stored in ECM memory, they will be displayed in the same manner. For more information on testing with codes, refer to the CEC PFI TESTS/CODES article in this section.
3. To exit diagnostic mode, turn ignition off and remove jmper wire from ALDL connector.

DIAGNOSTIC MATERIALS

Note. The charts described in the following paragraphs are arranged later in this article, by engine size and fuel system type.

DIAGNOSTIC CHARTS

The diagnostic charts are used to find and repair problems which the on-car diagnostics have found. These charts include

1. Charts which test the reliability of the self-diagnostic system.
2. Charts which help fix problems which are "SERVICE ENGINE SOON" light related.
3. Charts which test the computerized fuel control system performance.
4. Charts which help fix a problem when the on-car diagnostics don't work.
5. ENGINE CRANKS BUT WON'T RUN charts. Refer to the appropriate TROUBLE SHOOTING chart in the CEC TESTS W/O CODES article in this section.
6. Charts where a stored trouble code leads you to a particular problem. See ECM TROUBLE CODE DEFINITION and DIAGNOSTIC AIDS in this section. Charts which are used because the FIELD SERVICE MODE CHECK found a problem.

Note. Although there are many charts connected with computer diagnosis, only 2 charts are needed to prove system is operating properly. Normally, only 3 charts are necessary to find a problem, if one exists.

DIAGNOSTIC AIDS

Diagnostic aids (located in each "trouble code" chart box for each system) are additional tips used to help diagnose trouble codes when inspected circuit checks out okay. Diagnostic aids may help lead to a definitive solution to that trouble code problem. For more information on testing with codes, refer to the CEC PFI TESTS/CODES article in this section.

FIELD SERVICE MODE CHECK (FUEL INJECTED MODELS)

On fuel injected models, "SERVICE ENGINE SOON" light will indicate operational mode of engine if ALDL is grounded while engine is running. In closed loop mode, "SERVICE ENGINE SOON" light will flash at a rate of one flash per second. In open loop, light will flash at a rate of 2.5 flashes per second. If light is off all or most of the time, a lean exhaust is indicated. If light is on all or most of the time, a rich exhaust is indicated.

This test confirms proper operation of fuel system and verifies closed loop operation. Clear codes and perform this test after any repair is completed. For more information on testing with codes, refer to the CEC PFI TESTS/CODES article in this section. When performing this check, always engage parking brake and block DRIVE wheels. The parking brake on front-wheel drive models does NOT hold the drive wheels.

Note. On some engines, oxygen sensor will cool off after only a short period of time while engine is idling. This will cause engine to go into open loop. To restore closed loop mode, run engine at part throttle several minutes and accelerate from idle to part throttle several times.

SPECIAL DIAGNOSTIC TOOLS

Note. Special "Scan" testers plugged into the ALDL may be used to read trouble codes and check voltages in the system on the serial data line (terminal "E" on EFI and terminal "M" on EFI with P-4 systems). These testers can save a great deal of time. For more information on testing with codes, refer to the CEC PFI TESTS/CODES article in this section. For more information see SCAN TESTER USAGE and SCAN TESTER - TEST DATA PARAMETERS table in this article.

The computerized engine control system is most easily diagnosed using a "Scan" tester, however, other tools may aid in diagnosing problems if a "Scan" tester is unavailable. These tools are: a tachometer, a dwell meter, test light, ohmmeter, digital voltmeter with 10-megohm impedance (minimum), vacuum pump, vacuum gauge, fuel injector test lights (TBI and PFI) and 6 jumper wires 6" long (one wire with female connectors at both ends, one wire with male connector at both ends and 4 wires with male and female connectors at opposite ends). A test light, rather than a voltmeter, must be used when indicated by a diagnostic chart.

Note. If engine operation seems to change when dwell meter is connected to Green wire, remove dwell meter and use another type. A few brands are not compatible with computerized engine control system.

When engine is at operating temperature and idling, dwell meter needle should vary between 10-50 degrees. This indicates closed loop operation. Before engine reaches operating temperature, dwell should be fixed between 10-50 degrees, indicating open loop operation. If after reaching normal operating temperature dwell is fixed between 10-50 degrees, less than 10 degrees or more than 50 degrees, refer to appropriate CHART A - DWELL FIXED diagnostic chart for that system.

SCAN TESTER USAGE

Note. Prior to connection of scan tester to vehicle, diagnostic system should be checked to determine if system is operating properly and if information received by scan tester will be accurate. This is done by performing appropriate DIAGNOSTIC CIRCUIT CHECK for that system. If vehicle does not pass diagnostic circuit check, information received by scan tester may be invalid. CCC Scan tester is a specialized tester which, when plugged into ALDL, can be used to diagnose on-board computer control stems by providing instant access to circuit voltage information without need to crawl under dash or hood to back-probe sensors and connectors.

Scan testers cut down diagnostic time dramatically by furnishing input data (voltage signals) which can be compared to specification parameters. See SCAN TESTER - TEST DATA PARAMETERS table. They also furnish information on output device (solenoids and motors) status. Status parameters, however, are only an indication that output signals have been sent to devices by the ECM. It does not indicate if devices have responded properly to that signal. This will need to be verified at output device using a voltmeter or test light.

Note. Code 12 should always exist when ALDL is grounded with key on and engine not running but may not be indicated by all makes of scan tester.

If trouble codes are not present, this is not an indication that there is not a problem. CCC related problems are about 20 percent codes and 80 percent driveability. Sensors that are out of specification WILL NOT set a trouble code but WILL cause driveability problems. Use of a scan tester is easiest method of checking sensor specifications and other data parameters. Tester is also useful in finding intermittent wiring problems by wiggling wiring harnesses and connections (key on, engine off) while observing data parameters. See the SCAN TESTER - TEST DATA PARAMETERS table below.

Note. Information obtained by scan tester is only as accurate as the tester itself. If erroneous voltage signals are suspected, it will be necessary to verify tester information using a digital voltmeter and wiring schematic. If non-existent codes are in evidence, turn ignition off, remove tester, turn ignition on and ground ALDL "DIAGNOSTIC TERMINAL". If same codes are not flashed by "SERVICE ENGINE SOON" light that were indicated by scan tester, tester cannot be used on vehicle and information obtained by it will not be guaranteed accurate.

SCAN TESTER - TEST DATA PARAMETERS

Note. Information in the following tables is typical readings taken on vehicle with engine idling, upper radiator hose hot, closed throttle, transmission in Park or Neutral, "closed loop" status achieved and all accessories off (except as noted in tables). Data parameters are updated every 1 1/4 seconds. On systems using P-4 computers, parameter updates are virtually instantaneous. Not all devices & systems are used on all models.

THROTTLE BODY INJECTION

Note. This ECM voltage chart can be used with a digital voltmeter to help save time in diagnosis. Voltages on the car being tested my vary slightly from these due to battery or alternator charging level.

DIAGNOSTIC CIRCUIT CHECK

The Diagnostic Circuit Check is an organized approach for identifying fuel injection problems using the Assembly Line Data Link (ALDL). This communication link can provide diagnostic information for display on any "Scan" tester designed for this purpose.

If the "Scan" tester is not operating, check tester on another vehicle. If okay, the cigar lighter socket should be checked for 12 volts and a good ground. With the ignition on, if the "Scan" tester reads "NO DATA" or "NO ALDL", check the serial data wire for an open or short to ground. Also check for an open diagnostic "test" terminal "B". Refer to appropriate CHART A1 schematic for circuit wiring reference. With the ignition on, the serial data line should vary between 2-5 volts and the diagnostic line should have about 5 volts present. See SCAN TESTER USAGE and SCAN TESTER - TEST DATA PARAMETERS table in this article.

Diagnostic Circuit Check. Scheme 244

CHART A1 - NO "SERVICE ENGINE SOON" ("SES") LIGHT

"SERVICE ENGINE SOON" light should be on steady when ignition is on and engine is not running. Battery voltage is supplied directly to the bulb. The ECM turns the light on by grounding circuit No. 419 at the ECM.

If both the "keep alive" memory and the battery voltage supply are lost or the ignition feed is not present, the "SERVICE ENGINE SOON" light will not come on.

Engine Runs Okay, Check The Following

1. Faulty light bulb.
2. Circuit No. 419 has an open.
3. Fuel gauge fuse is blown. This will result in no stop, oil or alternator warning lights.

Engine Cranks But Will Not Run, Check The Following

1. Continuous battery power, fuse or fusible link is open.
2. ECM fuse has a open.
3. Battery circuit No. 340 to ECM is open.
4. Ignition circuit No. 439 to ECM is open.
5. Poor plug connection at ECM.

Flow Chart A1 & Schematic, No "SES" Light ("F" & "Y" Bodies). Scheme 245

Flow Chart A1 & Schematic, No "SES" Light ("F" & "Y" Bodies). Scheme 246

CHART A2 - NO ALDL/WON'T FLASH CODE 12 "SES" LIGHT ON STEADY

"SERVICE ENGINE SOON" light should be on with ignition on and engine not running. Battery voltage is supplied directly to the bulb. With the diagnostic terminal grounded, the light should flash a Code 12, followed by any other trouble codes stored in memory. A steady light indicates a short to ground in light control circuit No. 419, or an open in circuit No. 451.

Note. Test numbers refer to test numbers on diagnostic chart.

1. If there is a problem with the ECM that causes a "Scan" tester not to read serial data, the ECM should not flash a Code 12. If Code 12 is flashing, check for a short in circuit No. 451. If Code 12 does flash, be sure that "Scan" tester is working properly on another vehicle. If "Scan" tester is functioning properly and circuit No. 461 is okay, PROM, MEM-CAL or ECM may be causing the "NO ALDL" symptom.
2. If the light goes off when the ECM connector is disconnected, circuit No. 419 is not shorted to ground.
3. Checks for an open in diagnostic circuit No. 451.
4. At this point the wiring to the "SERVICE ENGINE SOON" light is okay. The problem could be a faulty ECM, PROM or MEM-CAL. If Code 12 does not flash, the ECM should be replaced using the original PROM or MEM-CAL. Replace PROM or MEM-CAL only after trying a new ECM.

Flow Chart A2 & Schematic ("F" & "Y" Bodies). Scheme 247

Flow Chart A2 & Schematic ("F" & "Y" Bodies). Scheme 248

CHART A3 - CRANKS/WON'T RUN (5.0L/5.7L "F" BODY)

This chart assumes that battery condition and engine cranking speed are okay, and there is adequate fuel in the tank.

Note. Test numbers refer to test numbers on diagnostic chart.

Test Steps For Chart 1 of 2

1. A "SERVICE ENGINE SOON" light, is a basic test to determine if there is 12 volts to the ECM. "NO ALDL" may be due to an ECM problem. CHART A2 will diagnose the ECM. If TPS is greater than 2.5 volts, the engine may be in the "clear flood" mode, which will cause starting problems. The engine will not start without reference pulses. "Scan" tester should read RPM (reference) while cranking.
2. No spark may be caused by one of several components related to the ignition system. CHART C4 will cover all problems related to the causes of a no spark condition.
3. The test light should blink, indicating that the ECM is controlling the injectors. How bright the light blinks is not important.
4. Use Fuel Pressure Gauge (J 34730-1). Wrap a shop towel around the fuel pressure tap to absorb any fuel leakage that may occur when installing the gauge.

Test Steps For Chart 2 of 2

1. Checks for 12 volts to injectors. Due to the injectors being wired in parallel, there should be a light on at both terminals.
2. Checks continuity of circuits No. 467 and 468.
3. All checks made to this point would indicate that the ECM is at fault, however, there is a possibility of circuits No. 467 or 468 being shorted to a voltage source either in the engine harness or in the injector harness.

An EGR valve sticking open can cause a low air/fuel ratio during cranking. Unless engine enters "clear flood" at the first indication of a flooding condition, it can result in a no start. Check for fouled plugs.

a defective cold start circuit or water in fuel line can cause a no start condition in cold weather. See CHART A9. A defective MAF sensor may cause a no start or a stall after start. To determine if the sensor is causing the problem, disconnect it. The ECM will then use a default value for the sensor. If the condition is corrected and the connections are okay, replace the sensor.

Also check that injectors on both sides of engine will cause a test light to blink. If not okay, check injector fuses. If all checks are okay, see TROUBLE SHOOTING in the article CEC TESTING W/O CODES (TROUBLE SHOOTING) article in the ENGINE PERFORMANCE section.

To test for this condition, disconnect all injectors. Turn ignition on. Probe circuits No. 467 and 468 on the ECM side of injector harness with a test light connected to ground (test one injector harness on each side of engine). There should no light. If light is on, repair short to voltage. If okay, check resistance of the injectors. Resistance should be 10 ohms or more.

Check injector harness connector. Be sure terminals are not backed out of connector and contacting each other. If all is okay, replace ECM.

Chart A3 (1 of 2), 5.0/5.7L "F" & "Y" Body: Cranks/Won't Run. Scheme 249

Chart A3 (2 of 2), 5.0/5.7L "F" & "Y" Body: Cranks/Won't Run. Scheme 250

CHART A7 - FUEL SYSTEM DIAGNOSIS

With the ignition on, the ECM will turn on the in-tank fuel pump. It will remain on as long as the engine is cranking or running, and the ECM is receiving HEI distributor reference pulses.

If there are no reference pulses (cranking or running), the ECM will shut off the fuel pump within 2 seconds. If fuel pump relay fails, a back-up oil pressure switch will energize the fuel pump when oil pressure reaches about 4 psi.

The fuel pump delivers fuel to the fuel rail and injectors, then to the pressure regulator, where system pressure is controlled to about 30-44 psi (2.1-3.0 kg/cm 2 ) when the engine is running. Excess fuel is returned to the fuel tank via the fuel return line.

Note. Test numbers refer to test numbers on diagnostic chart.

1. Use Fuel Pressure Gauge (J 34730-1). Wrap a shop towel around the fuel pressure tap to absorb any fuel leakage that may occur when installing the gauge. With the ignition on and engine off, fuel pressure should about 40-47 psi (2.8-3.2 kg/cm 2 ). This pressure is controlled by spring pressure within the regulator assembly.
2. When the engine is idling, manifold vacuum is high and is applied to the fuel regulator diaphragm. This will overcome regulator spring pressure, open fuel tank return passage and lower fuel pressure. Idle pressure will vary somewhat depending on barometric pressure, however, the pressure idling should be less, indicating proper pressure regulator control.
3. Pressure that continues to fall is caused by one of the following conditions: In-tank fuel pump check valve not holding. Pump coupling hose or pulsator leaking. Fuel pressure regulator valve leaking. Injector(s) sticking open.
4. Check for an injector sticking open by checking for a fouled or saturated spark plug. If a leaking injector can not be determined by a fouled or saturated spark plug, the following procedure should be used: Remove plenum, cold start valve and fuel rail bolts. Reconnect cold start valve. Connect a hose to valve nozzle and insert into a gasoline container. Lift fuel rail out just enough to leave injector nozzles in the ports. Turn key on to pressurize fuel system. DO NOT start engine. Lift each side of rail up and check for injector leaking.
5. See HOW TO USE THIS TROUBLE SHOOTING ARTICLE in the article «CEC TESTING W/O CODES (TROUBLE SHOOTING)»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#cec-testing-wo-codes-trouble-shooting) in the ENGINE PERFORMANCE section.

1. If fuel pressure is less than 40 psi (2.8 kg/cm 2 ) check the following: System has regulated pressure but pressure is less than 40 psi (2.8 kg/cm 2 ). Amount of fuel to injectors okay, but pressure is too low. Fuel system will run lean and may set Code 44. Also, vehicle is hard starting cold with overall poor performance. Restricted fuel flow that causes pressure drop. Normally a vehicle with a fuel pressure of less than 24 psi (1.6 kg/cm 2 ) at idle will not be driveable, however, if the pressure drop occurs only while driving, the engine will normally surge then stop as pressure begins to drop rapidly.
2. Restricting the fuel return line allows the fuel pump to develop its maximum pressure (dead head pressure). When battery voltage is applied to the pump test terminal or fuel pump relay, pressure should be greater than 60 psi (4.1 kg/cm 2 ).
3. This test determines if the high fuel pressure is due to a restricted fuel return line or a pressure regulator problem.

Flow Chart (1 of 2), Fuel System Diagnosis. Scheme 251

Flow Chart (1 of 2), Fuel System Diagnosis. Scheme 252

Flow Chart (2 of 2) - Fuel System Diagnosis. Scheme 253

CHART A9 - COLD START VALVE (5.0/5.7L "F" & "Y" BODIES)

The cold start valve is used to provide additional fuel during the crank mode to improve cold starts. This circuit is necessary because when engine coolant temperature is low, injector pulse width is not long enough to provide the needed amount of fuel for cold start.

This circuit is completely independent of the ECM. The circuit is activated only in the crank mode. The power is supplied directly from the starter solenoid and is protected by a fuse. The system is controlled by a cold start thermo time switch which provides a ground path for the valve during cranking when engine coolant is less than 95°F (35°C).

The cold start thermo time switch consist of a bi-metallic contact which opens at a specified coolant temperature. This bi-metallic switch is also heated by the circuit winding in the switch. This allows the valve to energize for a maximum of 8 seconds even at coolant temperatures as low as -4°F (-20°C). The time the switch will stay closed (1-8 seconds) varies with coolant temperature. In other words, as the coolant temperature goes up, the cold start valve "on" time goes down.

Note. Test numbers refer to test numbers on diagnostic chart.

1. Disconnecting the distributor 4-way connector will disable the other injectors. The amount of pressure drop depends on the temperature of the engine. This test could also be performed by removing the 2 injector fuses.
2. This test will determine the resistance through the switch to ground.

Chart A9 Schematic - 5.0/5.7L "F/Y" Bodies: Cold Start Valve. Scheme 254

Flow Chart A9 - 5.0/5.7L "F/Y" Bodies: Cold Start Valve. Scheme 255

Flow Chart A9 - 5.0/5.7L "F/Y" Bodies: Cold Start Valve (1 Of 2). Scheme 256

Flow Chart A9 - 5.0/5.7L "F/Y" Bodies: Cold Start Valve (2 Of 2). Scheme 257

5.0L VIN F & 5.7L VIN 8, "F" Body Camaro - Component Locations. Scheme 258

5.0L VIN F & 5.7L VIN 8, "F" Body Firebird - Component Locations. Scheme 259

ECM Terminal Identification, 5.0L (VIN F) & 5.7L (VIN 8). Scheme 260

Wiring Diagram, 5.0L (VIN F) & 5.7L (VIN 8). Scheme 261

See also:
• CEC TESTING W/O CODES (TROUBLE SHOOTING)