TROUBLE CODE DIAGNOSIS
The following abbreviations will be used in this section:
TPS - Throttle Position Sensor ECM - Electronic Control Module ISC - Idle Speed Control HEI - High Energy Ignition MAP - Manifold Absolute Pressure (Sensor) BARO - Barometric Pressure (Sensor) ECC - Electronic Climate Control MAT - Manifold Air Temperature (Sensor) CTS - Coolant Temperature Sensor MPG - Miles Per Gallon (Display Panel) EGR - Exhaust Gas Recirculation MD - Modulated Displacement MDA - Modulated Displacement Amplifier
The dash mounted "CHECK ENGINE" light is used to inform the technician of detected system malfunctions or abnormalities. The light goes out automatically of the fault clears (intermittent). However, the ECM stores the trouble code associated with the detected failure until the diagnostic system, is "Cleared" or until 20 ignition switch (on-off) cycles have occurred without the fault reappearing.
Proper operation of the light is as follows:
1. The light is normally off. 2. A bulb check is preformed when the ignition is in the "On" and "Crank" positions. When the engine starts, the bulb goes out. 3. The light comes on and stays on when a constant malfunction is detected. 4. If a malfunction is intermittent, the light will go out when the malfunction is not present. The light will come on each time a malfunction is detected (may flicker). 5. The light stays on when the system is displaying the diagnostic routine.
The dash mounted digital display panel, normally used for the ECC system, can be temporarily directed to display trouble codes stored in the ECM.
HOW TO "ENTER" DIAGNOSTIC MODE
To enter diagnostic mode, proceed as follows:
1. Turn the ignition "ON". 2. Depress the "OFF" and "WARMER" buttons on the ECC panel simultaneously and hold until "--" appears. "88" will then be displayed which indicated the beginning of the diagnostic readout. 3. Trouble codes will be displayed on the digital ECC panel beginning with the lowest numbered code. Note that the MPG panel goes blank when the system is displaying as the diagnostic mode.
HOW TO "CLEAR" TROUBLE CODES
Trouble codes stored in the ECM's memory may be cleared (erased) by entering the diagnostic mode and then depressing the "OFF" and "HI" button simultaneously. Hold until "00" appears. After "00" is displayed the ECM will display "70". Turn the ignition off for at least 10-seconds before re-entering the diagnostic mode.
HOW TO "EXIT" DIAGNOSTIC MODE
To get out of the diagnostic mode, depress any of the ECC "function" keys (Auto, Econ, etc. except Rear Defog) or turn ignition switch off for 10 seconds. Trouble codes are not erased when this is done. The temperature setting will reappear in the display panel.
DIAGNOSIS PROCEDURE
When the check engine light turns on, it indicated that a malfunction has occurred for which a trouble code has been stored. The trouble code can be displayed on the ECC control panel. The malfunction may or may not result in abnormal engine operation.
To determine which system(s) has malfunctioned, proceed as follows:
1. Turn the ignition "ON" for 5 seconds. 2. Depress the "OFF" and "WARMER" buttons on the Electronic Climate Control panel simultaneously and hold until "--" appears. 3. The numerals "88" should then appear. The purpose of "88" is to check that all segments of the display are working. Diagnosis should not be attempted unless the entire "88" appears as this could lead to misdiagnosis (Code 31 could be Code 34 with two segments of the display inoperative, etc.). 4. If trouble codes are present, they will be displayed on the digital ECC panel as follows: 1. The lowest numbered code will be displayed for approximately two seconds. 2. Progressively higher numbered codes, if present will be displayed consecutively for two seconds intervals until the highest code present has been displayed. 3. "88" is again displayed. 4. Parts a b and C above will be repeated a second time. 5. when the trouble codes have been displayed, code 70 will then be displayed. Code 70 indicates that the ECM id ready for the next diagnostic feature to be selected. 5. If no trouble codes are present, "88" will be displayed for a longer period of time, and then the ECM will display code 70. Code 70 indicates that the ECM is ready for the next diagnostic feature to be selected.
1980's Diagnostic Codes The following codes are programmed into the ECM
Code Circuit Affected 00 (E00) No PCM systems faults 12 (E12) No TACH Signal 13 (E13) O2 Sensor Not Ready 14 (E14) Shorted Coolant Sensor 15 (E15) Open Coolant Sensor 16 (E16) Generator Voltage Out Of Range 17 (E17) Crank Signal Circuit High 18 (E18) Open Crank Signal Circuit 19 (E19) Fuel Pump Circuit High 20 (E20) Open Fuel Pump Circuit 21 (E21) Shorted Throttle Position Sensor Circuit (DFI) Wide Open Throttle (WOT) Position Sensor Circuit (all others) 22 (E22) Open Throttle Position Sensor Circuit 23 (E23) EST/Bypass Circuit Shorted or Open (DFI) Mixture Control (M/C) Solenoid Open (Carbureted) MAT Sensor Circuit - Low Temp (TBI/all others) 24 (E24) Vehicle Speed Sensor (VSS) Failure 25 (E25) Modulated Displacement Failure (v8-6-4) EST/Bypass Circuit Shorted or Open (HT4100) MAT Sensor Circuit - High Temp (TBI/all others) 26 (E26) Shorted Throttle Switch Circuit 27 (E27) Open Throttle Switch Circuit 28 (E28) Open Fourth Gear Circuit 29 (E29) Shorted Fourth Gear Circuit 30 (E30) Idle Speed Control Circuit 31 (E31) Shorted MAP Sensor Circuit (DFI) Canister Purge Problem (all others) 32 (E32) Open MAP Sensor Circuit (DFI/TBI) BARO Sensor Circuit Problem (Carbureted) 33 (E33) MAP/BARO Sensor Correlation (DFI) Shorted MAP Sensor Circuit (all others) 34 (E34) Vacuum Sensor/MAP Hose (DFI) Open MAP Sensor Circuit (all others) 35 (E35) Shorted BARO Sensor Circuit (DFI) Idle Speed Control Circuit Shorted (all others) 36 (E36) Open BARO Sensor Circuit 37 (E37) Shorted MAT Sensor Circuit 38 (E38) Open MAT Sensor Circuit 39 (E39) TCC Engagement Problem 41 (E41) Electronic Spark Timing (EST) Problem 42 (E42) Electronic Spark Timing (EST) Circuit Open 43 (E43) Electronic Spark Control (ESC) Problem 44 (E44) O2 Sensor Lean 45 (E45) O2 Sensor Rich 51 (E51) PROM Insertion Fault 52 (E52) ECM Memory Reset Indicator 53 (E53) Distributor Signal Interrupt (HT4100) ECM Unit Fault (V6 Models) EGR Valve Vacuum Problem (all others) 54 (E54) Mixture Control (M/C) Solenoid Shorted 55 (E55) ECM/Oxygen Sensor Fault 60 (E60) Drive (ADL) Switch Circuit 61 (E61) Set and Resume Switch Circuit 62 (E62) Car Speed Exceeds Maximum Limit 63 (E63) Car and Set Speed Tolerance Exceeded 64 (E64) Car Acceleration Exceeds Maximum Limit 65 (E65) Coolant Temperature Exceeds Maximum Limit 66 (E66) Engine RPM Exceeds Maximum Limit 67 (E67) Shorted Set Or Resume Circuit 70 System Ready - Switch Tests 71 Brake Light Switch 72 ISC Throttle Switch 73 Drive (ADL) Switch 74 Back-Up Lamp Switch 75 Cruise On/Off Circuit 76 Set/Coast Circuit 77 Resume/Acceleration Circuit 78 Instant/Average MPG Button 79 Reset MPG Button 80 A/C Clutch Circuit 88 Display Check (-.1.8.8) 90 System Ready To Display Engine Data 95 System Ready for Acuator Cycling 96 Actuator Cycling 97 MD Cylinder Solenoid Cycling 00 All Diagnostic Complete
1980's Diagnostic Codes The following codes are programmed into the BCM
Code Circuit Affected F00 No BCM System Faults F10 Outside Air Temperature Circuit Problem F11 A/C High Side Temperature Circuit Problem F12 A/C Low Side Temperature Circuit Problem F13 In-Car Temperature Circuit Problem F19 Blower motor failure F32 BCM to ECM date transfer problem F40 Air Mix Door Problem F41 Cooling Fans Problem F46 Low A/C Refrigerant Condition Warning (1/2 charge) F47 Very Low A/C Refrigerant Condition Warning (1/4 charge) F48 Very Low A/C Refrigerant Pressure Condition F49 A/C High Side Temperature Too High (temperature exceeds 200°F) F50 Coolant Temperature Too High (exceeds 259°F)
Engine Data Display Procedure
Code "70" must be displayed on the ECC panel before engine data can begin. To display engine data slide the cruise control instrument panel switch from the ON position to the OFF position (1982 model year cars push "RESET" button the on the MPG display) the display code will advance from "70" to "90". To display the next parameter depress the "INSTANT/AVERAGE" button on the MPG panel. When the last parameter/data is reach the display will change to "95."
Engine Data Display
Parameter No. Parameter Value Units 01 TPS (Throttle Angle) XX Degrees 02 MAP (Manifold Air Pressure) XX kPa (KiloPascals) 03 BARO (Barometric Air Pressure) XX kPa (KiloPascals) 04 Coolant Temperature XX 0=-40C 99=150C (Degrees Celsius) 05 MAT (Manifold Air Temperature XX 0=-40C 99=150C (Degrees Celsius) 06 Injector Pulse Width X.X MSec (Milliseconds) 07 O2 Sensor .XX Volts 08 Spark Advance XX Degrees 09 Ignition Cycles XX Key Cycles 10 Open/Closed-Loop Indicator X 0=Open Loop 1=Closed Loop (HT4100 battery voltage) 11 Battery Voltage X.X Volts - Will Not Display 10's Digit (HT4100 engine RPMs) 12 Vehicle Speed (HT4100) 13 Prom ID (HT4100)
On cars equiped with an "outside temperature" button on the ECC, ECM operating mode can be switched between closed loop vs. open loop mode by depressing this button. With the LED illuminated ECM operates in a "Closed Loop Mode" - with the LED off ECM is in "Open Loop Mode."
ECM O2 Throttlet TCC output 4th A/C operating sensor switch input output gear input clutch mode input input input output ---------------------------------------------------------------------------------------------- Light on Closed loop Rich Closed throttle TCC enabled In 4th gear A/C Clutch enabled Light off Open loop Lean Open throttle TCC disabled Not in 4th gear A/C Clutch disabled
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