Feedback Carburetor Tests W/codes Chevrolet Chevette I

DIAGNOSIS & TESTING

Diagnosis of the CCC system is done in the following order

1. Ensure that all engine systems NOT related to the CCC are fully operational. DO NOT proceed with testing unless you are sure all other problems have been fixed.
2. Enter diagnostic mode and record trouble codes flashed by "CHECK ENGINE" light. Exit diagnostic mode.
3. Distinguish between "hard" or "intermittent" trouble codes.
4. If trouble codes were displayed, go to Diagnostic Circuit Check chart. Follow instructions given there.
5. If no trouble codes were recorded, go to Drive Complaint Sheet and follow instructions given there.
6. After any repairs are made, perform System Performance Check. Clear any trouble codes.

Note. The following paragraphs explain the procedures involved in performing the steps outlined above.

The ECM stores component failure information for CCC system under a related trouble code which can be recalled for diagnosis and repair. When recalled, these codes will be displayed by flashes of CHECK ENGINE" lamp. Codes are displayed starting with lowest numbered code. Only codes in which a related malfunction has occurred will be displayed.

Note. Example of trouble codes is as follows: "FLASH", "FLASH", "FLASH", pause, "FLASH", "FLASH" followed by a longer pause identifies trouble code "32". First series of flashes indicates first digit of trouble code; second series of flashes indicates second digit of trouble code.

Scheme 30

1. Turn ignition on (engine off). "CHECK ENGINE" lamp should glow. Locate Assembly Line Data Link (ALDL) connector attached to ECM wiring harness under instrument panel. Insert spade lug terminal across "TEST" terminal and "GROUND" terminal. (Scheme 30) (Scheme 30): ALDL Connector Terminal Locations
2. "CHECK ENGINE" lamp 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, then if any trouble codes are stored in ECM memory, they will be displayed in same manner.
3. Trouble codes will be displayed from lowest to highest numbered code (3 times each) and be repeated as long as the "TEST" terminal of ALDL connector is grounded.

CLEARING TROUBLE CODES

To clear memory of trouble codes, turn ignition on and ground TEST" lead at ALDL connector. Turn ignition off and remove ECM fuse from fuse block for 10 seconds. Remove "TEST" lead ground.

EXITING DIAGNOSTIC MODE

To exit diagnostic mode, turn ignition off and remove spade lug terminal from ALDL connector.

Note. The terms "enter diagnostics" and "exit diagnostics" will be used periodically throughout this section. Follow the procedure for entering diagnostic mode when instructed to "enter diagnostics". Follow the procedure for exiting diagnostic mode when instructed to "exit diagnostics".

FAILURE CODE DETERMINATION

During any diagnostic procedure, "hard failure" codes MUST be distinguished from "intermittent failure" codes. Diagnostic charts CANNOT be used to analyze "intermittent failure" codes, except as noted under Diagnostic Procedure. To determine "hard failure" codes and "intermittent failure" codes, proceed as follows

1. Turn ignition on and enter diagnostics. Read and record all stored trouble codes. Exit diagnostics and clear trouble codes. NOTE: Trouble codes will be recorded on "T" cars only with engine running. Turning ignition off after any trouble codes have been set will erase all codes.
2. Apply parking brake and place transmission in neutral man. trans.) or "P" (auto. trans.). Block drive wheels. Start engine. CHECK ENGINE" lamp should go out. Run warm engine at specified curb idle for 2 minutes and note "CHECK ENGINE" light. NOTE: Grounding "TEST" terminal with engine running will force engine to operate in closed loop mode if engine is warm and oxygen sensor is hot. If "CHECK ENGINE" lamp does not glow while in closed loop, CCC system is operating properly.
3. If "CHECK ENGINE" lamp comes on, enter diagnostics, read and record trouble codes. This will reveal "hard failure" codes. Codes 13", "15", "24", "35", "44", "45" and "55" may require road test to reset "hard failure" after trouble codes were cleared.
4. If "CHECK ENGINE" lamp does not come on, all stored trouble codes were "intermittent failures", except as noted under Diagnostic Procedure.

Note. Trouble code "15" malfunction will only display after 5 minutes of engine operation. Trouble code "12" will display only during time of no reference pulses received by ECM; it will never be stored as a malfunction.

BASIC DIAGNOSTIC PROCEDURES

The CCC system should be considered as a possible source of trouble on engine performance, fuel economy and exhaust emission complaints ONLY after normal checks (which apply to a vehicle without CCC) have been performed.

Diagnosis of CCC system consists of 3 types of initial checks: Diagnostic Circuit Check, Driver Complaint Check and System Performance Check/Field Service Mode Check. Any of these checks may lead to a chart for locating source of problem or indicate no problem on that check and refer to another check.

If there is no trouble in CCC system, all 3 checks will result in that conclusion. The checks and their procedures are as follows

Note. If vehicle exhibits performance problems and no codes are set, refer to System Performance Chart (carbureted models)/Field Service Mode Check (EFI models). Components recorded by trouble codes generally do not cause performance problems when no codes are stored in ECM memory.

DIAGNOSTIC CIRCUIT CHECK

1. If complaint is "CHECK ENGINE" lamp related, this check will lead to most likely problem area, if malfunction exists. Enter diagnostics and record stored trouble codes. Begin diagnosis with lowest numbered code which is displayed and refer to appropriate trouble code chart.
2. If code "51" is displayed, refer to PROM removal and installation in this article for diagnosis of this code. If codes "54" or "55" are displayed with another code, always refer to diagnostic chart for code "54" or "55" first, then proceed to next lowest numbered code.

Note. Any time codes "51", "54" or "55" are displayed with another code, start with "50-series" code first, then proceed to lowest numbered code.

DRIVER COMPLAINT CHECK

1. If complaint is not "CHECK ENGINE" lamp related, this check will lead to most likely problem area. However, first make checks that would normally be made for the complaint on a vehicle without CCC system.
2. Follow instructions in diagnostic chart and repair malfunction. After repair, perform System Performance Check/Field Service Mode Check.

SYSTEM PERFORMANCE CHECK (CARBURETED MODELS ONLY)

1. This check verifies that CCC system is functioning correctly. This check should always be made after any repair on CCC system.
2. When performing this check, always engage parking brake and block DRIVE wheels. Parking brake on front-wheel drive models does not hold drive wheels. On engines equipped with Varajet carburetors E2SE Model), remove bowl vent line at carburetor and plug hose at carburetor during check and reconnect it after the check is complete.
3. On some engines, the 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.

FIELD SERVICE MODE CHECK (EFI MODELS ONLY)

1. This test confirms proper operation of fuel system and verifies Closed Loop operation. Clear codes and perform this test after any repair is completed.
2. When performing this check, always engage parking brake and block DRIVE wheels. Parking brake on front-wheel drive models does not hold drive wheels.
3. On some engines, the 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.

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

DIAGNOSTIC TOOLS

1. The CCC system does not require special tools for diagnosis. A dwell meter, tachometer, test light, ohmmeter, digital voltmeter with 10 megohms impedance (minimum), vacuum pump, vacuum gauge and 6 jumper wires 6" long (1 wire with female connectors at both ends; 1 wire with male connectors at both ends; 4 wires with male and female connectors at opposite ends) are only tools necessary for diagnosis.
2. A test light, rather than a voltmeter, must be used when indicated by diagnostic chart.
3. A dwell meter is used to measure the time that mixture control solenoid is on or off. This gives an indication of how the system is working and how rich or lean the mixture is. The dwell meter is set for 6-cylinder scale on ALL engines, regardless of how many cylinders the engine has.
4. Dwell meter is connected to Green connector located near the carburetor. This connector will not be connected to any circuit EXCEPT when you are testing with the dwell meter. DO NOT allow terminal wire to come in contact with any ground source, including rubber hoses. 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 CCC system.
5. When engine is at operating temperature and idling, dwell meter needle will move up and down on scale, between 10-50°. This indicates "Closed Loop" operation. If the needle does not move, "Open Loop" operation is indicated.

Location of CCC System Components. Scheme 31

ECM TROUBLE CODE IDENTIFICATION

Trouble Code Identification Chart. Scheme 32

Flow Chart - System Performance Check Chart. Scheme 33

Flow Chart - System Performance Check Chart. Scheme 34

Flow Chart - Diagnostic Circuit Check Chart. Scheme 35

Flow Chart - Diagnostic Circuit Check Chart. Scheme 36

ENGINE PERFORMANCE PROBLEM - ODOR, SURGE, FUEL ECONOMY OR EMISSION PROBLEM

1. If the "CHECK ENGINE" light is not on, normal checks that would be performed on cars without the system should be done first.
2. If the alternator or coolant light is on with the "CHECK ENGINE" light, they should be diagnosed first.
3. Inspect for poor connections at coolant sensor, mixture control solenoid, etc. Also check for poor or loose vacuum hoses and connections. Repair as necessary.
4. If there is an intermittent "CHECK ENGINE" light, but no trouble code is stored, check the following: Check connection in Circuit No. 11 between the battery and ECM. Check ECM Terminal No. 1 to engine ground. Check ECM Terminal No. 19 to distributor, including tach filter. Check for an open diode across the A/C compressor clutch.
5. If the customer is experiencing poor full throttle performance, refer to CHART 5 - TPS ENRICHMENT CHECK.
6. If the customer is complaining of a cold operation problem, see CHART 3 - CTS CKT CHECK.

ALL OTHER COMPLAINTS

For any other complaints, do the SYSTEM PERFORMANCE CHECK with engine warmed to normal operating temperature.

Chart 1 - Dwell Fixed 10°-50°. Scheme 37

Chart 2 - Dwell Fixed Over 50° (Rich Exhaust Indication). Scheme 38

Chart 3 - Coolant Temperature (CTS) Sensor Circuit Check. Scheme 39

Chart 4 - "CHECK ENGINE" Light Inoperative. Scheme 40

Chart 5 - TPS Enrichment Check. Scheme 41

Chart 6 - Won't Flash Code 12. Scheme 42

Air Management Check - With Electric Divert And Electric Switching Valve. Scheme 43

Flow Chart, Code 12 - No Distributor Reference Pulse To ECM. Scheme 44

Flow Chart, Code 12 - No Distributor Reference Pulse To ECM. Scheme 45

Engine Cranks But Will Not Run. Scheme 46

Flow Chart, Code 15 - Open Coolant Temperature Sensor (CTS) Circuit. Scheme 47

Note. If trouble code 15 and 21 are displayed, go to trouble code 21 chart first.

Flow Chart, Code 15 - Open Coolant Temperature Sensor (CTS) Circuit. Scheme 48

Flow Chart, Code 21 - Throttle Position Sensor (TPS) Ckt - (Open or Misadjusted). Scheme 49

Flow Chart, Code 21 - Throttle Position Sensor (TPS) Ckt - (Open or Misadjusted). Scheme 50

Flow Chart, Code 23 - Mixture Control (M/C) Solenoid Circuit (Open or Grounded). Scheme 51

Flow Chart, Code 23 - Mixture Control (M/C) Solenoid Circuit (Open or Grounded). Scheme 52

Flow Chart, Code 44 - Lean Exhaust Indication. Scheme 53

Flow Chart, Code 44 - Lean Exhaust Indication. Scheme 54

Flow Chart, Code 45 - Rich Exhaust Indication. Scheme 55

Note. If M/C solenoid does not click with ignition on, test terminal grounded and there is no trouble code 23, check for sticking M/C solenoid.

Flow Chart, Code 45 - Rich Exhaust Indication. Scheme 56

Flow Chart, Code 51 - Prom Error Indication. Scheme 57

Flow Chart, Code 51 - Prom Error Indication. Scheme 58

PROM is either installed incorrectly, defective, or has the wrong part number. Check for proper installation and application. If Part number is correct and problem still exists, replace PROM.

CHART C1 - ECM REPLACEMENT CHECK CHART

In order to reduce incidents of repeat ECM failure, a revised ECM diagnostic procedure is available. Beginning in 1982, most ECMs are equipped with Integrated Circuits (IC) in place of separate transistors to operate various controlled components.

These ICs, called Quad-Drivers (QDR), have 4 separate outputs, meaning that each QDR can operate up to 4 different components. An inoperative QDR can result in ECM output becoming open or shorted to ground. Often, all 4 outputs of a QDR will fail, even if just one QDR circuit is faulty.

Refer to the following tables to determine which ECMs contain QDRs. Since this procedure is not applicable to ECMs which do not contain QDRs, those ECMs are not listed.

Performing the diagnostic flow chart will identify an inoperative QDR. Once the circuit is identified, it must be repaired to eliminate repeat ECM failure. This diagnostic procedure must be used when "Replace ECM" is the conclusion of any procedure.

ECM QDR IDENTIFICATION (CARBURETED)

Scheme 59

ELECTRONIC CONTROL MODULE (ECM) R & I

Remove ECM mounting hardware. Disconnect electrical connectors and ground strap. Remove ECM. To install ECM, reverse removal procedure and ensure ground strap is securely attached.

Note. The ECM may be located at right side kick panel, glove compartment area or center console area.

Removal

1. Remove ECM as previously described. Remove sheet metal screw holding access cover closed and remove access cover. Using a small flat tip screwdriver, place blade at PROM carrier reference end between edge of opening in case and underside of protruding lip of carrier. Apply prying force and force side of carrier up as far as possible. Repeat procedure on other reference end lip.
2. Using prying force explained in step 1), force opposite end of carrier up as far as possible. Grasp carrier with thumb and forefinger. Gently rock carrier from side to side while applying upward force and remove PROM.

Scheme 60

1. Before installing new PROM, be sure part number agrees with removed PROM. Ensure molded "half-round" depression of PROM is at same end as "squared-off" symmetrical end of carrier and that PROM is centered in carrier. NOTE: If PROM is installed backwards and ignition is turned on, PROM will be destroyed and must be replaced. (Scheme 60): Replacing PROM In Electronic Control Module (ECM)
2. Position carrier squarely over PROM socket with squared-off" symmetrical end of carrier aligned with small notch in socket. Press down firmly on top of carrier and press down on body of PROM with narrow blunt tool. Squarely seat PROM in socket by alternately pressing down on either end of PROM.
3. Replace access cover and reinstall ECM. Reconnect electrical connectors and start engine. Enter diagnostics and check for Flow Chart, code "51". If Flow Chart, code "51" does not appear, PROM is correctly installed.
4. If code "51" does appear, PROM is not fully seated, is installed backwards, has bent pins, or is defective. Remove ECM and fully seat PROM. If pins are bent, remove PROM, straighten pins and reinstall PROM. If pins break or crack during straightening process, replace PROM. If PROM is installed backwards, replace PROM.

OXYGEN SENSOR R & I

Raise and support vehicle (if required). Disconnect electrical connector at harness. Spray threads of oxygen sensor with penetrating oil and allow to soak for 5 minutes. Carefully remove oxygen sensor.

Note. DO NOT attempt to reinstall an oxygen sensor. Reinstallation of a sensor without special glass bead thread coating may require complete replacement of exhaust system.

Install new oxygen sensor and tighten to 30 ft. lbs. When installing new oxygen sensor, do not remove glass bead coating (anti-seize compound) from threads or install with any type of sealant. Reconnect electrical connector. Ensure oxygen sensor boot is 5/16" away from the wrench fitting of the oxygen sensor.

THROTTLE POSITION SENSOR (TPS) R & I

Removal and installation require removal of carburetor or throttle body unit.

MAP/BARO Or Vacuum Sensor Location (Location may also be in passenger compartment.). Scheme 61

TORQUE CONVERT CLUTCH (TCC) SOLENOID HIGH GEAR SWITCH R & I

Removal and installation requires disassembly of transmission.

Note. Removal and installation of any solenoids, switches or sensors not listed is accomplished by disconnecting the wiring harness and removing or detaching the device. To install, reverse removal procedure.

Minimum Function CCC System Wiring Diagram (1000 & Chevette). Scheme 62