3800 VIN [c] - ECM Tests W/codes Oldsmobile Toronado IV

PRELIMINARY PROCEDURES

Prior to any hard part diagnosis, various system checks should be performed.

1. Check to see if "Service Engine Soon" light is working. If this light fails to light when the ignition is turned on and engine is not running, problem could be in power supply circuits to these systems. The "Self-Diagnostic Check" will direct you to the appropriate diagnostic chart.
2. Can "Service Mode" be accessed? If CRT is not operable, self-diagnostics are not possible. In this case, the "Self-Diagnostic System Check" will direct you to the appropriate diagnostic chart.
3. Are there any service code(s) displayed? If a trouble code is identified using self-diagnostics, a problem has been detected by the system which can be corrected by following the appropriately numbered fault code. Codes with the prefix "E", are ECM codes. Codes with the prefix "B", are BCM codes.
4. Perform a visual check of the entire system. Check the suspected wiring and components. Inspect hoses that are difficult to see beneath the compressor, generator, etc. Inspect all related wiring for opens, improper connections, burned or chafed spots, pinched wires, contact with sharp edges or contact with hot exhaust manifolds.

Trouble Codes

During the process of controlling various subsystems, the ECM and BCM continually monitor operating conditions for possible system malfunctions. By comparing system conditions against standard operating limits, certain circuit and component malfunctions can be detected.

A 3-digit numerical "Trouble Code" is stored in computer memory when a problem is detected. These trouble codes can later be displayed to aid technician in diagnosing the system. This display of diagnostic trouble codes can only be accessed in the "Service Mode".

Certain system malfunctions cause computer controlled diagnostic messages and/or telltales to appear, indicating that service is required. When a subsystem circuit exceeds preprogrammed limits, a system malfunction is indicated and the BCM provides certain back-up functions known as "Failsoft". A typical "Failsoft" action would be the substitution of a fixed input value when a sensor is detected to be open or shorted.

ENTERING "SERVICE MODE"

Note. Operating vehicle in the "Service Mode" for extended time periods (1/2 hour or longer), without the engine running, will cause battery drain, and possibly relate false diagnostic information and/or a no-start condition.

Turn ignition switch to "ON" position. Touch "OFF" and "WARM" buttons on ECC control panel simultaneously, and hold until a segment check is displayed on the instrument panel and ECC control panel (usually about 3 seconds). (Scheme 120)

Electronic Climate Control (ECC) Panel (Toronado). Scheme 120

CLIMATE CONTROL IN SERVICE MODE

When in the "Service Mode", the climate control will continue to operate in whatever setting it was in prior to the "Service Mode". Even though the display may change as the buttons are touched, the previous operating mode is remembered and will resume after entering "Service Mode".

After trouble codes have been displayed, the "Diagnostic Mode" can be used to perform several tests on different systems, one at a time. A specific system may be selected for testing, or a segment check can be performed.

SYSTEM SELECTION

Following trouble code display, the first available system will be displayed (i.e. ECM). While selecting a system to test, any of the following actions may be taken to control the display

1. Pressing the "OFF" button will stop the system selection process and return the display to the beginning of trouble code sequence.
2. Pressing the "LOW" fan button will display the next available system selection. This allows all system selections to be displayed. The list of systems can be repeated following the display of the last system.
3. Pressing the "HIGH" fan button will select the displayed system for testing. At this point the first available test type will appear with the selected system above it.
4. Pressing the "BI-LEVEL" button will exit diagnostics and return to normal IPC and ECC operation.

TEST TYPE SELECTION

Having selected a system, the first available test type will be displayed (i.e. "ECM DATA"). When selecting a specific test type the following are available actions to be taken

1. Pressing the "OFF" button will stop the test type selection process and return to the next available selection.
2. Pressing the "LOW" fan button will display the next available test type for the selected system. This allows all available test types to be displayed for selection.
3. Pressing the "HIGH" fan button will select the displayed test type. At this point the display will either indicate whether the selected test type is in progress, or the first of several tests will appear.
4. Pressing the "BI-LEVEL" button will exit diagnostics.

TEST SELECTION

Selection of the "DATA", "INPUTS", or "OUTPUTS" test types will result in the first available test being displayed. If "==" message appears, this test is not allowed with the engine running. Turn engine off and repeat sequence.

The last 4 characters of the display will contain a test code to identify the selection. The first 2 of these characters are letters which identify the system and the test type (i.e. ED for ECM DATA) and last 2 characters numerically identify the test (i.e. ED01 for Throttle Position). When selecting a specific, the following actions may be taken to control the display

1. Pressing the "OFF" button will stop the test selection process and return the display to the next available test type for the selected system.
2. Pressing the "LOW" fan button will display the next smaller test number for the selected test type. If this button is touched with the lowest test number displayed, the highest test number will then appear.
3. Pressing the "HI" fan button will display the next larger test number for the selected test type. If this pad is touched with the highest test number displayed, the lowest test number will then appear.

Upon selecting an "OVERRIDE" test function, current operation will be represented as a percentage of its full range. This value will be displayed on the ECC panel. The display will alternate between "-" and the normal program value. This alternating display is a reminder that function is not currently being overridden.

Pressing the "WARM" or "COOL" buttons on the ECC panel begins the override, at which time the display will no longer alternate to "-". Pressing the "WARM" button increases the value, while pressing the "COOL" button decreases the value. Normal program control can be resumed in one of 3 ways.

1. Selection of another override test will cancel the current override.
2. Selection of another system (ECM, BCM or IPC) will cancel the current override.
3. Overriding the value beyond either extreme (0 or 99) will display "-" momentarily and then jump to the opposite extreme. If the button is released while "-" is being displayed, normal program control will resume and the display will begin alternating.

The override test type is unique in that any other test type within the selected system may be active at the same time. After selecting an override test, pressing the "OFF" button will allow selection of another test type (DATA, INPUTS or OUTPUTS). The ECC panel will continue to display the selected override. By selecting another test type and test, while at the same time pressing the "WARM" or "COOL" button, it is possible to monitor the effect of the override on different vehicle parameters.

Toronado Service Mode Operation Sequence. Scheme 121

CODE RESET SELECTION

Selecting the reset codes will result in the message "CLEAR ECM CODES?" or "CLEAR BCM CODES?", depending on which system was being tested. At this point, the following action may be taken

1. Pressing the "OFF" button will stop the test selection process and return the display to the next available test type for the selected system.
2. Pressing the "LO" fan button will display the next test type.
3. Pressing the "HI" fan button will select "CLEAR CODES". A message "ECM CODES CLEARED" or "BCM CODES CLEARED" will appear to indicate those codes have been cleared from memory.
4. Pressing the "BI-LEV" button will exit diagnostics.

ECM Snapshot

Selection of "SNAPSHOT?" test type while in the ECM system level, will result in the message "SNAPSHOT TAKEN" being displayed with the selected system name preceding it. This message will appear for 3 seconds to indicate that all ECM data and inputs have been stored in memory. After 3 seconds, the display will proceed to the first available snapshot test type, "SNAP DATA?". While selecting a snapshot test type, any of the following actions may be taken to control the display

1. Pressing the "OFF" button on the ECC panel will stop the test type selection process and return the display to the next available system selection.
2. Pressing the "LO" button will display the next available snapshot test type. This allows the display to be stepped through all available choices. This list of snapshot test types can be repeated following the display of the last choice.
3. Pressing the "HI" button with "SNAP DATA?" or "SNAP INPUTS?" displayed will select that test type. At this point the display is controlled as it would be for non-snapshot data and input displays, however, all values and status information represents memorized vehicle conditions.
4. Pressing the "HI" button with "SNAPSHOT?" displayed, will again display the "SNAPSHOT TAKEN" message to indicate that new information has been stored in memory. Access to this information is obtained the same as previously described.

EXITING "SERVICE MODE"

To exit the "Service Mode", press the "BI-LEV" button. Trouble codes are not erased when this is done. Any mode button will exit diagnostics, however, the "BI-LEV" button was chosen for consistency.

DATA DISPLAYS

When trouble shooting a malfunction, the ECM and BCM data display can be used to compare the problem vehicle, with a vehicle that is functioning properly. The following is a brief summary of each parameter.

ECM DATA DISPLAY CODES

INPUT DISPLAYS

When trouble shooting a malfunction, the ECM, BCM, or IPC input display can be used to determine if the switched inputs are properly interpreted. When one of the input tests is selected, the state of that device is displayed as "HI" or "LO". Basically, "HI" or "LO" represent the input terminal voltage for that circuit.

Also, the display indicates if the input changed state since it was last tested. If a change occurred, an "X" will appear next to the HI - LO indicator. If a change did not occur, an "O" will remain displayed. The "X" will only appear once per selected input.

ECM INPUT DISPLAY CODES

OUTPUT DISPLAYS

When trouble shooting a malfunction, the ECM and BCM output cycling can be actuated regardless of the inputs and normal program instructions. Once a test in outputs is selected, except for ECM IAC, the test will display "HI" or "LO" for 3 seconds in each state to indicate the command and output terminal voltage.

ECM OUTPUT DISPLAY CODES

OVERRIDE DISPLAYS

When trouble shooting a malfunction, the BCM override feature allows testing of certain system functions regardless of normal program instructions.

The override feature, or test type, is unique in that any other test type within the selected system may be active at the same time.

ECM OVERRIDE DISPLAY CODES

TROUBLE CODE DISPLAY

After the "Service Mode" is entered, any trouble codes stored in the computer will be displayed. ECM codes will be displayed first. If no ECM codes are stored, the IPC will display "NO ECM CODES". All ECM codes will be prefixed by an "E" (i.e. E013).

When all ECM codes have been displayed, BCM codes will be displayed. BCM codes mainly deal with body control functions, with climate control being one of its main features. BCM codes are prefixed with an "B" (i.e. B110). BCM codes can also be accompanied by "Current", indicating that the fault still exists. If no BCM codes exist, "NO BCM CODES" message will be displayed.

Both ECM and BCM codes are displayed in 2 second intervals starting at the lowest numbered code and ending at the highest. If the "LO" fan button is pressed anytime during the display of ECM and BCM codes, the display of codes will be by-passed. If at any time the "BI-LEVEL" button is pressed, the BCM will exit the "Service Mode" and go back to normal vehicle operation.

TROUBLE CODES DEFINITIONS

ECM TROUBLE CODE DEFINITIONS

DIAGNOSTIC CIRCUIT CHECK (*START HERE*)

The Diagnostic Circuit Check is an organized approach to identifying a problem created by an electronic control system malfunction, because it directs the service technician to the next logical step in diagnosing a complaint.

If after completing the diagnostic circuit check and finding the on-board diagnostics functioning properly and no trouble codes displayed, a comparison of "Typical Scan Values", for the appropriate engine, may be used for comparison. The "Typical Values" are an average of display values recorded from normally operating vehicles and are intended to represent what a normally functioning system would display.

Diagnostic Circuit Check. Scheme 122

CHART A1, "SERVICE ENGINE SOON" LIGHT INOPERATIVE

The "SERVICE ENGINE SOON" light is attached to the IPC. It is powered by ignition "1" circuit No. 439. The ECM completes the ground to turn the light on. The light will be on while the engine is not running. With the engine running, a steady light indicates an ECM code is set. When the engine is running and diagnostics are entered, a flashing light indicates the field service mode of the ECM. The system monitor button will not affect the "SERVICE ENGINE SOON" light.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step splits the circuit into 2 sections. A light on after grounding terminal "D", indicates the open is on the ECM side of the split. A light off, indicates the open is on the IPC side of the circuit.
2. If the test light did not light when connected between ECM terminal "2A6" and ground, the ECM will not be powered up. This is a result of an open or short to ground (blown fuse) in circuit No. 439.
3. This test checks if open is in the IPC or circuit No. 419. There should be battery voltage at IPC terminal "D2" when connected to terminal "C9". The test light should be on, indicating circuit No. 419 is complete through ALDL terminal "D" which has been jumpered to ground.
4. This test checks if the open is in the ECM or circuit No. 419. If the test light is on when ECM terminal "3C11" is grounded, the fault is in a poor terminal contact or a faulty ECM.

Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following

1. Poor Connection. Check at ECM pin No. "3C11" or IPC connector. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal to wire connections.
2. Damaged Harness. Inspect harness for damage. If harness appears okay, observe related connectors and wiring harness. A flickering light would indicate the intermittent fault location.

Chart A1, "Service Engine Soon" Light Inoperative. Scheme 123

CHART A2, "SERVICE ENGINE SOON" LIGHT ALWAYS ON

The "SERVICE ENGINE SOON" light is attached to the IPC. It is powered by ignition "1" circuit No. 439. The ECM completes the ground to turn the light on. The light will be on while the engine is not running. With the engine running, a steady light indicates an ECM code is set. When the engine is running and diagnostics are entered, a flashing light indicates the field service mode of the ECM. The system monitor button will not affect the "SERVICE ENGINE SOON" light.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step verifies that the light remains on with the engine running no ECM codes displayed.
2. Unplugging the ECM harness "AB" connector determines if the short to ground exists in the ECM or somewhere else in the circuit. If the "SERVICE ENGINE SOON" light remains on, the fault is not in the ECM.
3. This step removes the IPC to distinguish between a grounded IPC or a grounded circuit No. 419. If the test light is on when connected between IPC terminals "C9" and "D2", circuit No. 419 is shorted to ground.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following

1. Poor Connection. Check at ECM pin No. "3C11" or IPC connector. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal to wire connections.
2. Damaged Harness. Inspect harness for damage. If harness appears okay, observe related connectors and wiring harness. A flickering light would indicate the intermittent fault location.

Chart A2 "Service Engine Soon" Light Won't Go Out. Scheme 124

CHART A3, ENGINE CRANKS BUT WILL NOT RUN

The C(3)I system uses waste spark method of spark distribution. In this type of ignition system, ignition module triggers No. 1 and 4 coil, resulting in both No. 1 and 4 spark plugs firing at the same time. The No. 1 cylinder is on compression stroke at the same time that No. 4 is on exhaust stroke, resulting in a lower energy requirement to fire No. 4 spark plug. This leaves the remaining high voltage to fire No. 1 spark plug.

The sequential fuel injection type of fuel delivery system utilizes 6 separate injector "driver" circuits to activate the 6 fuel injectors. While cranking, ECM activates all 6 injector "driver" circuits simultaneously (all at one time). After a calibrated engine RPM is reached, and a good camshaft signal has been received by the ECM, the injection mode of operation is changed to sequential (sprayed in spark plug firing order).

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

1. This test verifies that "SES" light operation, TPS, and coolant sensor signals are normal. A blinking injector test light verifies that ECM is monitoring C(3)I reference signal and attempting to pulse injectors.
2. The cam and crank sensors have been verified as functioning properly. Performing a fuel pressure test will differentiate between fuel related or ignition system problem.
3. The 8 terminal injector harness connector must be unplugged to avoid flooding of engine and fouling of spark plugs. By testing for spark on plug leads 1, 3 and 5, each ignition coil's ability to produce at least 25,000 volts is verified.
4. Checking faulty coil's control circuit using a test light, will determine whether coil is faulty, or module's internal driver for that coil is at fault.
5. This test checks for battery voltage at circuit No. 1039. If voltage was present, "light off" test result was caused by no activation pulse reaching injector connector from ECM.
6. If fuse was blown, check circuit No. 839, which includes fuel pump relay, fuel pump and wiring, to determine cause of high current flow.
7. Test light to 12 volts simulates a reference signal to the ECM. This results in an injector test light flash with each contact of the test light probe to terminal "D". Various injector clicks (pulses) will be heard. It may take up to 3 probe contacts to flash test light. If test light flashes, circuit No. 430, ECM and injector driver circuits are functioning properly.
8. If crank sensor signal circuit terminal "A" is momentarily jumpered to ground circuit terminal "C", and engine is cranked without turning ignition off, the response should be an injector test light flash. This is due to an artificial "Sync Signal" being transmitted to C(3)I module. This allows generation of the 3x reference signal to ECM terminal "1D8", and ECM to activate injector driver circuit.
9. This test verifies proper sync signal circuit voltage of 6-9 volts, and a proper ground from C(3)I module to terminal "C" of sensor connector.
10. Determines if reason for incorrect voltage reading was due to fault in circuit No. 645 or faulty C(3)I module.
11. Jumping crank sensor harness terminals "A" and "C" together, simulates a sync signal to the C(3)I module. By jumpering crank sensor harness terminals "B" and "C" together, a crank signal is simulated. This signal will then cause the ECM to energize the fuel pump relay for 2 seconds (it should click on and off), and several, if not all, injectors should be heard clicking on and off.
12. Verifies a proper crank signal circuit voltage of 6-9 volts and a good ground from the C(3)I module to terminal "C" of the sensor connector.
13. Determines if reason for incorrect voltage reading was due to a fault in circuit No. 643, an open in circuit No. 645, or a faulty C(3)I module.

Chart A3, Engine Cranks But Will Not Run (1 of 4). Scheme 125

Chart A3, Engine Cranks But Will Not Run (2 of 4). Scheme 126

Chart A3, Engine Cranks But Will Not Run (3 of 4). Scheme 127

Chart A3, Engine Cranks But Will Not Run (4 of 4). Scheme 128

CHART A5, FUEL SYSTEM ELECTRICAL TEST

When ignition is turned on, ECM will energize the fuel pump relay, which completes the circuit to the in-tank fuel pump. It will remain on as long as the engine is cranking or running, and ECM is receiving C(3)I reference pulses. If there are no reference pulses, the ECM will de energize the fuel pump relay within 2 seconds after key is turned on and engine is not running.

The fuel pump will deliver fuel to the fuel rail and injectors, then to the pressure regulator, where the system pressure is controlled. Excess fuel pressure is by-passed back to fuel tank. When engine is shut off, the pump can be turned on by applying battery voltage to test terminal located in engine compartment. Improper fuel system pressure may contribute to one or all of the following symptoms

1. Cranks but won't run.
2. Code E044 or E045.
3. Cuts out, may feel like ignition problem.
4. Hesitation, loss of power or poor fuel economy. NOTE: Test numbers refer to test numbers on diagnostic chart.

1. If the fuse is blown, a short to ground in circuits No. 120 and 839, or the fuel pump itself is cause of problem.
2. Determines if fuel pump circuit is being controlled by the ECM. The ECM should energize the fuel pump relay. When the engine is not cranking or running with key on, ECM should de energize the relay within 2 seconds after ignition is turned on.
3. This test turns on fuel pump if circuit No. 120 wiring is okay. If pump runs, problem is basic fuel delivery.
4. This test will determine if a short to ground in circuit No. 120 caused fuse to blow. To prevent an incorrect diagnosis, ensure fuel pump is disconnected before test.
5. Checks for short to ground in fuel pump relay harness circuit No. 839.
6. Checks for open in the fuel pump relay ground, circuit No. 450.
7. Determines if the ECM is in control of the fuel pump relay through circuit No. 465 (terminal "A").
8. The fuel pump control circuit includes an engine oil pressure switch with a separate set of normally open contacts. The switch closes at about 4 psi of oil pressure and provides a second battery voltage feed path to the fuel pump. If relay fails, the pump will run using battery voltage supplied by closed oil pressure switch. This step checks the oil pressure switch, ensuring that it provides battery voltage to the fuel pump should pump relay fail. A failed pump relay will result in extended engine crank time because of time required to build sufficient oil pressure to close oil pressure switch, and turn on fuel pump. There may be circumstances when relay has failed, but engine will not crank fast enough to build sufficient oil pressure to close switch. This, or a faulty oil pressure switch, can result in an "ENGINE CRANKS BUT WON'T RUN" condition.

Chart A5, Fuel System Electrical Test (1 of 2). Scheme 129

Chart A5, Fuel System Electrical Test (2 of 2). Scheme 130

CHART A7, FUEL PRESSURE TEST

1. Install Fuel Pressure Gauge (J-34730-1) to pressure tap. Wrap a shop towel around fuel pressure gauge tap to absorb any small amount of fuel leakage that may occur when installing gauge. Connect fuel tank harness connector. Start engine. With ignition on and engine running, pump pressure is regulated by spring pressure and throttle body vacuum within the pressure regulator assembly. Turn ignition off for 10 seconds. Pressure should not leak down after fuel pump is shut off.
2. When engine is idling, vacuum is high and is applied to the fuel pressure regulator diaphragm. This will overcome regulator spring pressure, resulting in a lower fuel pressure.
3. The application of 12-14 in. Hg vacuum to the pressure regulator should result in reduced fuel pressure.
4. Fuel pressure that leaks down may be caused by one of the following conditions: In-tank fuel pump check valve not holding. Pump coupling hose leaking. Fuel pressure regulator valve leaking. Injector sticking open. The fuel pump will deliver fuel to the fuel rail and injectors and then to the pressure regulator, where the system pressure is controlled. Excess fuel pressure is by-passed back to the fuel tank. The fuel pump test terminal is located in the engine compartment. Improper fuel system pressure may contribute to one or all of the following symptoms: Cranks but won't run. Code 44 or 45. Cuts out, may feel like ignition problem. Hesitation, loss of power, or poor fuel economy.
5. If fuel system has pressure, but is less than specification, condition may be caused by one of the following: Regulated pressure, but less than specification. The amount of fuel to injectors is okay, but pressure is too low. The fuel system will operate lean and may set Code 44. Also, hard starting cold and overall poor performance condition may exist. Restricted fuel flow causing pressure drop. Normally, vehicle with fuel pressure of less than 24 psi (1.7 kg/cm 2 ) at idle will not be driveable. If pressure drop occurs only while driving, engine will normally surge and shut off as pressure begins to drop rapidly.
6. 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, pressure should be greater than 75 psi (5.2 kg/cm 2 ).
7. This test determines if high fuel pressure is due to a restricted fuel return line or a pressure regulator problem.

Chart A7, Fuel Pressure Test (1 of 2). Scheme 131

Chart A7, Fuel Pressure Test (2 of 2). Scheme 132

CHART B1, RESTRICTED EXHAUST SYSTEM CHECK

Before any components are replaced, exhaust system must be checked for restrictions. Check at O2 sensor procedure may be used to diagnose condition, depending on engine or tool used.

Check at O2 Sensor

Remove O2 sensor. Install backpressure tester in place of O2 sensor as shown in illustration. After test is completed, ensure that O2 sensor threads are coated with anti-seize compound before installation.

Diagnosis

1. Start engine and bring to operating temperature. Raise engine speed to 2500 RPM and observe exhaust system backpressure gauge. Reading should not exceed 1.25 psi (.09 kg/cm 2 ).
2. If during step 1), specification is exceeded, exhaust system restriction is indicated.
3. Check complete exhaust system for collapsed pipe, heat distress and possible internal muffler failure.
4. If none of the conditions in step 4) exist, check for restricted catalytic converter. Replace if necessary.

Chart B1, Restricted Exhaust System Check. Scheme 133

CODE E013, OPEN OXYGEN SENSOR CIRCUIT

Code E013 is set when engine has run for 40 seconds, coolant temperature is above 109°F (42.5°C), voltage at terminal No. D7 of the ECM stays within a range of 350-550 mV, TPS is 6 percent above idle (.9-.10 volts), or condition lasts for 60 seconds consecutively. The ECM supplies a voltage of about .45 volt between terminals "3D2" and "3D3". (If measured with a 10-megaohm digital voltmeter, this may read as low as .32 volts.) The oxygen sensor varies the voltage within a range of about one volt if the exhaust is rich, down through about .10 volt if exhaust is lean.

The sensor is like an open circuit and produces no voltage when it is below 600°F (360°C). An open sensor circuit or cold sensor causes "open loop" operation.

Note. Test numbers refer to numbers on diagnostic chart.

1. Allowing engine to run under these conditions will give a normally operating oxygen sensor sufficient time to cause system to run "closed loop". If voltage at this point is holding steady at about 450 mV, then the fault is present and must be further analyzed.
2. This will determine if the sensor or the wiring is the cause of the Code E013.
3. In performing this test, use only a high impedance digital volt/ohmmeter. This test checks the continuity of circuits No. 412 and 413. If circuit No. 413 is open, the ECM voltage on circuit No. 412 will be greater than .6 volts (600 mV).

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following conditions

1. Poor Connection or Damaged Harness. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test. If connections and harness check okay, observe data ED15 display, O2 sensor voltage while moving related connectors and wiring harness, with warm engine running at part throttle in "Closed Loop". If the failure is induced, the O2 sensor voltage reading will change from its normal fluctuating voltage (greater than 600 mV and less than 300 mV) to a fixed value around 450 mV. This may isolate the location of malfunction.

Code E013, Open Oxygen Sensor Circuit. Scheme 134

CODE E014, COOLANT SENSOR TEMPERATURE TOO HIGH

The coolant temperature sensor uses a thermistor to control the signal voltage to the ECM. The ECM applies a voltage on circuit No. 410 to the sensor. When the engine is cold the sensor thermistor) resistance is high, therefore, the ECM will see high signal voltage.

As the engine warms to operating temperature, the sensor resistance becomes less, and the voltage drops. At normal engine operating temperature (85°C to 95°C), the voltage will measure about 1.5-2.0 volts.

Note. Test numbers refer to numbers on diagnostic chart.

1. Code E014 will set if signal voltage indicates a coolant temperature greater than 282°F (130°C) for .4 seconds.
2. This test will determine if circuit No. 410 is shorted to ground which will cause the conditions for Code E014. If Code E014 is set, the ECM will use 119°F (48.6°C) for fuel control.

Check for the following conditions

1. Poor Connection or Damaged Harness. Inspect ECM harness connectors for backed out terminal "3D4", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test. If connections and harness check okay, observe data ED04 display (coolant temperature) while moving related connectors and wiring harness. If the failure is induced, the coolant temperature display will change. This may help to isolate location of malfunction.
3. Shifted Sensor. The temperature-to-resistance value scale may be used to test the coolant sensor at various temperature levels to evaluate the possibility of a shifted (mis-scaled) sensor, which may result in driveability complaints.

Code E014, Coolant Sensor Temperature Too High. Scheme 135

CODE E015, COOLANT SENSOR TEMPERATURE TOO LOW

The coolant temperature sensor uses a thermistor to control the signal voltage to the ECM. The ECM applies a voltage on circuit No. 410 to the sensor. When the engine is cold the sensor thermistor) resistance is high, therefore, the ECM will see high signal voltage.

As the engine warms to operating temperature, the sensor resistance becomes less, and the voltage drops. At normal engine operating temperature (85°C to 95°C), the voltage will measure about 1.5-2.0 volts.

Note. Test numbers refer to numbers on diagnostic chart.

1. Code E015 will set if signal voltage indicates a coolant temperature less than -40°F (-40°C) for at least 2 seconds.
2. This test simulates a Code E014. If the ECM recognizes the low signal voltage (high temperature), and the CTS display reads 130°C, the ECM and wiring are okay.
3. This test will determine if circuit No. 410 is open. There should be 5 volts present at sensor connector if measured with a digital volt/ohmmeter. If Code E015 is set, the ECM will use 119°F 48.6°C) for fuel control.

Check for the following conditions

1. Poor Connection or Damaged Harness. Inspect ECM harness connectors for backed out terminal "3D4", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test. If connections and harness check okay, observe data ED04 display (coolant temperature) while moving related connectors and wiring harness. If the failure is induced, the coolant temperature display will change. This may help to isolate location of malfunction.
3. Shifted Sensor. The temperature-to-resistance value scale may be used to test the coolant sensor at various temperature levels to evaluate the possibility of a shifted (mis-scaled) sensor, which may result in driveability complaints.

A faulty connections, or an open in circuits No. 410 or 452 will result in a Code E015. If Code E023 is also set, check circuit No. 452 for faulty wiring or connections. Check terminals at sensor for good contact. Refer to INTERMITTENT PROBLEMS in the CEC TESTING W/O CODES (TROUBLE SHOOTING) article in this section.

Code E015, Coolant Sensor Temperature Too Low. Scheme 136

CODE E016, BATTERY VOLTAGE TOO HIGH

The ECM monitors battery or system voltage on circuit No. 480 to terminals "2B1" and "1C16". If the ECM detects voltage greater than 16 volts, it will turn the "SES" light on and set a Code E016 in memory.

Note. Test numbers refer to numbers on diagnostic chart.

1. Test generator output as outlined to determine proper operation of the voltage regulator. Run engine at moderate speed and measure voltage across the battery. If over 16 volts, repair generator.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following conditions

1. Poor Connection or Damaged Harness. Inspect harness connectors for backed out terminals "1C16" or "2B1", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test. If connections and harness check okay, observe data ED10 display, while moving related connectors. If the failure is induced, the battery voltage will abruptly change. This may help to isolate the location of the malfunction. An engine stall while manipulating the harness indicates that the ECM has lost voltage at terminal "1C16" or "2B1". Check for loose connectors in circuit No. 480.

Note. Charging battery with a battery charger and starting the engine may set a Code E016.

Code E016, Battery Voltage Too High. Scheme 137

CODE E021, TPS SIGNAL VOLTAGE HIGH

The Throttle Position Sensor (TPS) provides a voltage signal that changes with the position of the throttle valve. Signal voltage will vary from .4 volt at idle to 5 volts at wide open throttle. The TPS signal is one of the most important inputs used by the ECM for fuel control and for most of the ECM control outputs.

Note. Test numbers refer to numbers on diagnostic chart.

1. Code E021 will set under the following conditions occur: Engine is running and airflow is less than 15 Gm/sec. TPS signal voltage is greater than 2.5 volts. Code E033 or E034 not present at first start up. All conditions met for 5 seconds. With closed throttle, ignition on or engine at idle, voltage at terminal "3D13" should be .36-.44 volt. If not, TPS should be adjusted to specification.
2. With TPS sensor unplugged, TPS voltage should go low and Code E022 will set, if ECM and wiring is okay.
3. Probing circuit No. 452 with a test light checks sensor ground circuit. A faulty sensor ground circuit will cause a Code E021.

A on-board diagnostics data display ED01 reads throttle position in volts. With closed throttle, ignition on or at idle, voltage should be .36-.44 volt. If not, adjust TPS to specification. An open in circuit No. 452 will result in a Code E021. Check for the following conditions

1. Poor connections or damaged harness. Inspect ECM harness connectors for backed out terminal "3D13", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connections and damaged harness.
2. Intermittent test. If connections and harness checks out okay, monitor TPS voltage on data display ED01 while moving related connectors and wiring harness. If failure is induced, coolant temperature display will change. This may help to isolate location of malfunction.
3. TPS scaling. Observe TPS voltage display while depressing accelerator pedal with engine stopped and ignition on. Display should vary from closed throttle TPS voltage when throttle was closed, to greater than 4.5 volts when throttle is held at WOT position.

Code E021, TPS Signal Voltage High. Scheme 138

CODE E022, TPS SIGNAL VOLTAGE LOW

The Throttle Position Sensor (TPS) provides a signal voltage that changes relative to throttle angle. Signal voltage will vary from about .4 volt at idle to about 5 volts at wide open throttle. The TPS signal is one of the most important inputs used by the ECM for fuel control and for most of the ECM control outputs.

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

1. Code 22 will set if engine is running and TPS signal voltage is less than .2 volt for 4 seconds.
2. Simulates Code E021. If ECM recognizes high signal voltage, ECM and wiring are okay.
3. With closed throttle, ignition on or engine at idle, voltage at terminal "3D13" should be .36-.44 volt. If voltage is not okay, check TPS adjustment.
4. Simulates a high signal voltage. Checks circuit No. 417 for open.

The on-board diagnostics data display ED01 reads throttle position in volts. Voltage should increase at a steady rate as throttle is moved from WOT. An open or short to ground in circuit No. 416 or 417 will result in a Code E022. Check for the following conditions

1. Poor connections. Inspect ECM harness connectors for backed out terminal "3D13", improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection and damaged harness.
2. Intermittent test. If connections and harness checks out okay, monitor TPS voltage while moving related connectors and wiring harness. If failure is induced, coolant temperature display will change. This may help to isolate location of malfunction.
3. TPS scaling. Observe TPS voltage display while depressing accelerator pedal with engine stopped and ignition on. Display should vary from closed throttle TPS voltage when throttle was closed, to greater than 4.5 volts when throttle is held wide open.

Code E022, TPS Signal Voltage Low. Scheme 139

CODE E023, MAT SENSOR SIGNAL VOLTAGE HIGH

The Manifold Air Temperature (MAT) sensor uses a thermistor to control monitored voltage to the ECM. ECM applies and monitors about 5 volts on circuit No. 472 to sensor. When air temperature is cold, sensor resistance is high, therefore, ECM will see a high signal voltage. If air temperature is warm, sensor resistance is low and ECM will see low monitored voltage.

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

Code E023 will set if a signal voltage indicates a manifold air temperature less than -40°F (-4°C) for 4 seconds. Due to the conditions necessary to set a Code E023, the "Service Engine Soon" SES) light will stay only while fault is present.

1. The on-board diagnostics data display ED23 may not be used to diagnose this fault, due to the ECM transmitting "default" values. A Code E023 will set, due to an open sensor, wire or connection. This test determines if wiring and ECM are okay.
2. If resistance is greater than 25,000 ohms, replace sensor.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following conditions

1. Poor Connection or Damaged Harness. Inspect harness connectors for backed out terminals "3D11", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test. If connections and harness check okay, observe data ED23 display, while moving related connectors and wiring harness with warm engine running at part throttle in closed loop. If the failure is induced, the MAT display may change the 16°C default value to the proper ambient temperature reading. This may help to isolate location of the malfunction.

Code E023, MAT Sensor Signal Voltage High. Scheme 140

CODE E024, VEHICLE SPEED SENSOR (VSS) CIRCUIT

The VSS system incorporates 3 major components. They include the vehicle speed generator, the BCM, and the ECM. The vehicle speed generator is a permanent magnet assembly attached to the transaxle. As the vehicle moves, the generator creates a "sine wave" electrical pulse which is monitored by the BCM. In the BCM, this is amplified and "cleaned up" via the same process as used in a buffer. Part of this "cleaning up" involves changing the "sine wave" signal to a square wave" signal or on/off type of signal. By determining the length of time between the "ON" and "OFF" portions of the signal, the BCM can interpret the vehicle speed. It then transmits this data via circuit No. 437 to the ECM.

Because of the circuitry involved, it is highly unlikely that a Code E024 alone will be caused by a faulty VSS. However, a combination of Codes E024 and B124 could represent this. In the case of a Code B124 accompanying a Code E024, see the appropriate charts in the BCM section first.

To set a Code E024, the following conditions must exist

1. Engine speed must be between 1500-4000 RPM.
2. LV8 reading (Diagnostics Data ED23) between 40 and 150 counts.
3. Vehicle speed less than 3 MPH.
4. Gear selector not in Park or Neutral.
5. Above conditions met for 40 seconds. NOTE: Test numbers refer to numbers on diagnostic chart.

1. If a Code B124 is present also, refer to accompanying charts for diagnosis of B124 before attempting to diagnose E024.
2. If ECM data display ED12 (vehicle speed) displays zero MPH, the ECM is not receiving a VSS input from the BCM.
3. A zero MPH display at this point, indicates a fault which should have set a Code B124. Refer to that chart for the remainder of diagnosis. A display greater than zero, indicates a fault in circuit No. 437, faulty connections at the ECM or BCM, or a faulty ECM.

Code E024, Vehicle Speed Sensor (VSS) Circuit. Scheme 141

CODE E025, MAT SENSOR CIRCUIT (HIGH TEMPERATURE INDICATED)

The MAT sensor is a thermistor. ECM applies voltage (about 5 volts) on circuit No. 472 to sensor. When air temperature is cold, sensor (thermistor) resistance is high, therefore, the ECM will measure a high monitored voltage. If temperature air is warm, sensor resistance is low, ECM will measure a low voltage.

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

Code E025 will set if

1. Signal voltage indicates manifold air temperature greater than 275°F (135°C).
2. A vehicle speed is present.
3. Both of the above requirements are met for at least 30 seconds.

Due to the conditions necessary to set a Code E025, SES light will only stay on while fault is present.

1. Data display ED23 may not be used to diagnose this fault, due to ECM transmitting default (substitute) values, when fault is present. If voltage is greater than 4 volts, ECM and wiring are okay.
2. If resistance is less than 185 ohms, replace sensor.

MAT Sensor Circuit (High Temperature Indicated). Scheme 142

CODE E026, QUAD DRIVER (QDM) ERROR

The ECM is used to control several components such as those illustrated in the mini circuit schematic. ECM controls these devices through the use of a Quad Driver module (QDM). When the ECM is commanding a component on, the voltage potential of the output circuit will be low (near zero volts). When the ECM is commanding the output circuit to a component off, the voltage potential of the circuit will be high (near battery voltage). The primary function of the QDM is to supply the ground for the component being controlled.

Each QDM has a fault line which is monitored by the ECM. The fault line signal is available on the data stream for "Scan" tester equipment. The ECM will compare the voltage at the QDM based on accepted values of fault line. If the QDM fault detection circuit senses a voltage other than the accepted value, the fault line will go from a low signal on the data stream, to a high signal and a Code E026 will set if applicable.

Some QDM circuits will switch from low to high normally. Examples: QDM No. 2, if A/C pressure switch closes and turns on high speed coolant fan or QDM No. 3, if brake is depressed. These conditions are normal and no Code E026 is set. These are accepted conditions. A fault on QDM No. 2 will not set a Code E026, but diagnosis may be done by ensuring A/C is turned off. Some "Scan" tools will cause a false Code E026 to set if engine is running and service brake is depressed for over 30 seconds.

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

1. The ECM does not know which controlled circuit caused the Code E026. This chart will go through each of the circuits to determine which is at fault. This test also checks "SERVICE ENGINE SOON" light driver and "SERVICE ENGINE SOON" light circuit.
2. QDM fault symptoms: TCC inoperative, Code E039. EGR inoperative, Codes E063, E064 and E065. Coolant fan on low speed all the time of won't come on at all. Poor driveability due to 100 percent canister purge. NOTE: Test numbers refer to test numbers on diagnostic chart.
3. This test will determine which circuit is out of specification. All circuit, except "YC11", "SERVICE ENGINE SOON" light, "YC9", and hot light, should have battery voltage when key is on, engine not running. Diagnostic test terminal is not grounded.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following condition

1. Inspect ECM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.

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

1. 4) This test will determine if problem is the circuit of the component. As factory installed ECM is protected with an internal fuse, it is highly unlikely that ECM needs replacement.

Code E026, Schematic Quad Driver (QDM) Error. Scheme 143

Code E026, Flow Chart Quad Driver (QDM) Error (1 of 3). Scheme 144

Verify proper operation of "Service Engine Soon" by performing

Diagnostic Circuit Check

Code E026, Flow Chart Quad Driver (QDM) Error (1 of 3). Scheme 145

Code E026, Flow Chart Quad Driver (QDM) Error (2 of 3). Scheme 146

Code E026, Flow Chart Quad Driver (QDM) Error (2 of 3). Scheme 147

Code E026, Flow Chart Quad Driver (QDM) Error (3 of 3). Scheme 148

Note. Use wiring diagram for specific terminals to be tested.

Code E026, Flow Chart Quad Driver (QDM) Error (3 of 3). Scheme 149

CODE E027, E028 & E029, 2ND, 3RD & 4TH GEAR SWITCH DIAGNOSIS

Gear switches are located inside the transaxle. They are pressure operated switches, that are normally closed. The ECM supplies 12 volts through each selected circuit to switch. In any condition other than the specific gear application, signal line monitors low voltage or low potential. As road speed increases, hydraulic pressure is applied to specific gear clutches, and gear switch opens. During this time, ECM monitors high 12-volt potential and interprets this to indicate that gear is applied. The ECM uses gear signals to control fuel delivery (and TCC).

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

Code E027 will set under the following conditions

1. Circuit No. 581 indicates ground or closed switch when vehicle is in 4th gear operation.
2. Circuit No. 581 indicates an open (drive) when the engine is first started.

Code E028 will set under the following conditions

1. Circuit No. 108 indicates ground or closed switch when vehicle is in 4th gear operation.
2. Circuit No. 108 indicates an open (drive) when the engine is first started.

Code E029 will set under the following conditions

1. Circuit No. 446 indicates ground or closed switch when vehicle is in 4th gear operation.
2. Circuit No. 446 indicates an open (drive) when the engine is first started.

1. Digital Volt/Ohm Meter (DVOM) must be used. A test light will not light due to the very low current being supplied by the ECM.
2. Checks to see if circuit is grounded through switch.
3. Checks for a good, properly operating switch. Also checks circuit within transaxle for an improper ground.

An intermittent may be caused by a poor connection, incorrectly routed harness, rubbed through wire insulation or a wire broken inside insulation. Check for the following

1. Poor Connection, at ECM pins. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal to wire connection.
2. Misrouted Harness. Inspect wiring harness to ensure that it is not too close to high voltage wires, such as spark plug leads.
3. Damaged Harness. Inspect harness for damage. If harness appears okay, "Scan" while moving related connectors and wiring harness. A change in display would indicate the intermittent fault location.

2nd, 3rd & 4th Gear Switch Diagnosis. Scheme 150

CODE E031, PARK/NEUTRAL SWITCH CIRCUIT

The Park/Neutral (P/N) switch contacts are part of the neutral start switch and are closed to ground in Park or Neutral, and open in Drive. The ECM supplies ignition voltage through a current limiting resistor to circuit No. 434 and senses a closed switch when the voltage on circuit No. 434 drops to less than one volt. The ECM uses the P/N signal as one of the inputs to idle air control, EGR and VSS diagnostics.

Code 31 will set under the following conditions

1. If circuit No. 434 indicates P/N (grounded) while in Drive range and 4th gear TCC engaged, EGR would be inoperative, resulting in possible detonation.
2. If circuit No. 434 indicates Drive (open) at start up, a drop in idle may exist when gear selector is moved into Drive range.
3. If transaxle 4th gear switch has an intermittent open, ECM thinks vehicle is in 4th gear and will set Code E031. NOTE: Test numbers refer to test numbers on diagnostic chart.

1. Checks for a closed switch to ground in "PARK" position. Different types of "Scan" testers will read P/N differently. Refer to Scan" tester operators manual for type of display used for specific tester.
2. Checks for an open switch in drive range.
3. Ensure that on-board diagnostics EI74 indicates drive HI"), even while wiggling shifter. This will test for an intermittent or misadjusted switch in drive or overdrive range.

Code E031, Park/Neutral Switch Circuit. Scheme 151

CODE E034, MASS AIRFLOW SENSOR CIRCUIT

The Mass Airflow (MAF) sensor measures the flow of air which passes through it in a given time. The ECM uses this information to monitor the operating condition of the engine for fuel delivery calculations. A large quantity of air movement indicates acceleration, while a small quantity indicates deceleration or idle.

The MAF sensor produces a frequency signal, which cannot be easily measured. The sensor can be diagnosed using the procedures in this chart. Code E034 will set, when either of the following sets of conditions exists

1. Engine running.
2. No MAF sensor signal for 250 mS.
3. Above conditions for greater than 4 seconds. NOTE: Test numbers refer to test numbers on diagnostic chart.

1. This step checks to see if ECM recognizes a problem.
2. A voltage reading at sensor harness connector terminal "A" of less than 4 volts, or greater than 6 volts, indicates a fault in circuit No. 492 or poor connections.
3. Verifies that both ignition voltage and a good ground circuit are available.

Check for the following

1. Poor Connection, at ECM pin "3D10". Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal to wire connection.
2. Misrouted Harness. Inspect MAF sensor harness to ensure that it is not too close to high voltage wires, such as spark plug leads.
3. Damaged Harness. Inspect harness for damage. If harness appears okay, observe data display ED21 while moving related connectors and wiring harness. A change in display would indicate the intermittent fault location.

Code E034, Mass Airflow Sensor Circuit. Scheme 152

CODE E038, BRAKE SWITCH CIRCUIT

The ECM monitors the status of brake switch circuits through ECM terminal "BC4". Code E038 will set under the following conditions

1. Code 24 is not present.
2. Vehicle speed has been greater than 35 MPH and back to zero MPH several times.
3. Status of circuit No. 420 has not changed state (high or low). NOTE: Test numbers refer to test numbers on diagnostic chart.

1. This step checks for battery voltage available for circuit No. 420.
2. Checks fuse, switch and circuit for battery voltage.

Code E038, Brake Switch Circuit. Scheme 153

CODE E039, TORQUE CONVERTER CLUTCH (TCC) CIRCUIT

The ECM controls TCC operation by grounding circuit No. 422 through the QDM. Code E039 will set under the following conditions

1. Code E029 is not present.
2. Brake switch is closed (off).
3. TCC is commanded by ECM.
4. Vehicle is in 4th gear.
5. The engine speed to vehicle speed ratio is outside of its window of operation.
6. All of the above for a time greater than 30 seconds.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks availability of battery voltage on circuit No. 420.
2. Check fuse, brake switch and battery voltage circuit to the TCC solenoid.

Code E039, Torque Converter Clutch (TCC) Circuit. Scheme 154

CODE E041, CAM SENSOR CIRCUIT

Quick reference

1. (Scheme 156)for Code E041 flow chart.
2. (Scheme 155)for Code E041 supplemental wiring.

All Updated Information

All the Code E041 information here (including the flow chart) has been updated as per the General Motors Technical Service Bulletin (TSB) listed below. All outdated information has been discarded.

1. Oldsmobile 91-T-45

Circuit Description

During cranking, the ignition module monitors the dual crank sensor sync signal. The sync signal is used to determine the correct cylinder pair to spark first.

After the sync signal has been processed by the ignition module, it sends a fuel control reference pulse to the ECM. When the ECM receives this pulse it will command all six injectors to open for one priming shot of fuel in all cylinders.

After the priming, the injectors are left off for the next six fuel control reference pulses from the ignition module (two crankshaft revolutions). This allows each cylinder a chance to use the fuel from the priming shot.

During this waiting period, a cam pulse will have been received by the ECM. Now the ECM begins to operate the injectors sequentially based on true camshaft position.

However, if the cam signal is not present at start-up, a Code E041 will set and the ECM will start sequential fuel delivery in random pattern with a 1 in 6 chance that fuel delivery is correct.

Test Description

The numbers below refer to the circled numbers in the diagnostic flow chart.

1. This step verifies proper operation of circuits 633, 644, and 645. (Scheme 155)for circuit identification.
2. Step validates the integrity of Circuit 630 from the ignition module to the ECM. (Scheme 156)for circuit identification.
3. If the camshaft gear magnet is interfacing with the cam sensor the voltage reading will be zero, bumping engine will cause the condition to go away.
4. If the voltage reading of terminal "BC5" is constantly varying and connection to terminal "BC5" are good, the ECM is faulty.

An intermittent may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside the insulation.

Check for the following

1. Poor Connection or Damaged Harness: Inspect ECM harness connectors for backed out terminal "BC5", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test: If connections and harness check okay, monitor a digital voltmeter connected from ECM terminal "BC5" to ground while moving related connectors and wiring harness. If the failure is induced, the voltage reading will change. This may help to isolate the location of the malfunction.

Scheme 155

Scheme 156

Code E041 Flow Chart - Cam Sensor Signal. Scheme 157

Note. When probing connectors to measure voltages, use the connector test adapter kit J-35616 to make connections.

CODE E042, EST IGNITION CIRCUIT

The C(3)I module sends a reference signal to the ECM when the engine is cranking. When the engine is running less than 400 RPM, the C(3)I module controls ignition timing. When the engine speed exceeds 400 RPM, the ECM sends a 5 volt signal on the by-pass circuit No. 424 to switch timing to ECM control. An open or ground in the EST circuit will stall the engine and set a Code E042. The engine can be restarted but will run on module timing. The following conditions must be met to set a Code E042

1. Engine speed greater than 600 RPM with no EST pulse for 200 mS (open or grounded circuit No. 423).
2. ECM commanding by-pass mode (open or grounded circuit No. 424). NOTE: Test numbers refer to test numbers on diagnostic chart.

1. Checks to see if ECM recognizes a problem. If it does not set Code E042, it is an intermittent problem and could be due to a loose connection.
2. With ECM is disconnected, ohmmeter should be reading less than 200 ohms, which is the normal resistance of EST circuit through C(3)I module. A higher resistance would indicate a fault in circuit No. 423, poor C(3)I module connection, or faulty C(3)I module.
3. If test light was on when connected from 12 volts to ECM harness terminal "1C7", either circuit No. 424 is shorted to ground or C(3)I module is faulty.
4. Checks to see if C(3)I module switches when by-pass circuit is energized by 12 volts through test light. If C(3)I module actually switches, ohmmeter reading should shift to greater than 8,000 ohms.
5. Unplugging ignition module should cause ohmmeter to read as if it were monitoring an open circuit (infinite reading). If not, circuit No. 423 is shorted to ground.

An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Check for the following conditions

1. Poor Connection or Damaged Harness. Inspect ECM harness connectors for backed out terminals "1C7" or "1C8", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test. If connections and harness check okay, connect digital voltmeter from affected terminal to ground and move related connectors and wiring harness. If failure is induced, voltage reading will change.

Code E042, EST Ignition Circuit. Scheme 158

CODE E043, ELECTRONIC SPARK CONTROL (ESC) CIRCUIT

The knock sensor is used to detect engine detonation. The ECM will retard electronic spark timing based on the signal being received. The circuitry within the knock sensor causes the ECM's supplied 5 volt signal to be pulled down, so that under a no knock condition, circuit No. 496 would measure about 2.5 volts. The knock sensor produces an AC signal which rides on the 2.5 volts (DC voltage). The amplitude and signal frequency are dependent upon the knock level.

If circuit No. 496 becomes open or shorted to ground, voltage will either go greater than 3.5 volts or less than 1.5 volts. If either of these conditions are met for about 5 seconds, a Code E043 will stored.

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

1. Code E043 will set if: Coolant temperature is greater than 90°C. MAT temperature is greater than 0°C. High engine load based on LV8 and RPM. Voltage on circuit No. 496 goes greater than 3.5 volts or less than 1.5 volts. All of above conditions met for 5 seconds. If an audible knock is heard from the engine, repair internal engine problem, normally no knock should be detected at idle.
2. If tapping on engine lift hook does not produce a knock signal, try tapping engine closer to sensor before proceeding.
3. The ECM has a 5 volt pull-up resistor which should be present at knock sensor terminal.
4. This test determines if knock sensor is faulty or if ESC portion of the MEM-CAL is faulty.

Check circuit No. 496 for a potential open or short to ground. Check for proper installation of MEM-CAL. See INTERMITTENT PROBLEMS in the CEC TESTING W/O CODES (TROUBLE SHOOTING) article in this section.

Code E043, Electronic Spark Control (ESC) Circuit. Scheme 159

CODE E044, OXYGEN SENSOR CIRCUIT (LEAN EXHAUST INDICATED)

The ECM supplies a voltage of about .45 volt (450 mV) between terminals "3D2" and "3D3". If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt. The O2 sensor varies the voltage within a range of about one volt (1000 mV) if exhaust is rich, down through about .10 volt (100 mV) if exhaust is lean.

The sensor is like an open circuit and produces no voltage when it is less than about 600°F (360°C). An open sensor circuit or cold sensor will result in vehicle operating in open loop. Code E044 is set when the O2 sensor signal voltage on circuit No. 412 remains less than .2 volt for 60 seconds or more, and the system is operating in closed loop.

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

1. Running the engine at 1000 RPM keeps O2 sensor hot, so an accurate display voltage is maintained.
2. Opening O2 sensor wire should result in a voltage display of between 350 and 550 mV. If display is still fixed less than 350 mV, fault is a short to ground in circuit No. 412 or ECM is faulty.

Diagnostics Aids

Using the on-diagnostics data display ED20, observe the block learn values at different RPM and air flow conditions. If the conditions for Code E044 exists, the block learn values will be around 150. Check for the following conditions

1. Oxygen sensor pigtail may be mispositioned and contacting exhaust manifold.
2. Check for intermittent ground in wire between connector and sensor.
3. A Mass Airflow (MAF) sensor output that causes ECM to sense a lower than normal airflow will cause the system to go lean. Disconnect MAF sensor and if lean condition is eliminated, replace MAF sensor.
4. Perform injector balance test, see CHART C2A.
5. Water, even in small amounts, near in-tank fuel pump inlet can be delivered to injectors. Water causes a lean exhaust and can set Code 44.
6. System will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving vehicle at various road speeds and/or loads to confirm problem. See CHART A7.
7. If there is an exhaust leak, engine can cause outside air to be pulled into exhaust, across the oxygen sensor. Vacuum or crankcase leaks can cause a lean condition.
8. If all of the above checks are okay, replace oxygen sensor.

Code E044, Oxygen Sensor Circuit (Lean Exhaust Indicated). Scheme 160

CODE E045, OXYGEN SENSOR CIRCUIT (RICH EXHAUST INDICATED)

The ECM supplies a voltage of about .45 volt (450 mV) between terminals "3D2" and "3D3". If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt. The O2 sensor varies the voltage within a range of about one volt (1000 mV) if exhaust is rich, down through about .10 volt (100 mV) if exhaust is lean.

The sensor is like an open circuit and produces no voltage when it is less than about 600°F (360°C). An open sensor circuit or cold sensor will result in vehicle operating in open loop. Code E044 is set when the O2 sensor signal voltage on circuit No. 412 remains greater than .7 volt for 30 seconds and in closed loop and engine time after start is one minute or more. Also, if throttle angle is between 3 and 45 percent.

Using the on-diagnostics data display ED20, observe the block learn values at different RPM and air flow conditions. If the conditions for Code E045 exists, the block learn values will be around 115. Check for the following conditions

1. Fuel Pressure. System will go rich if pressure is too high. ECM can compensate for some increase in fuel pressure. If fuel pressure becomes too high, a Code E045 may be set. See fuel system diagnosis in CHART A7.
2. Rich Injector. Perform injector balance test, see CHART C2A.
3. Leaking Injector. See CHART A7 for diagnosis.
4. Check for contaminated fuel.
5. Canister Purge. Check for fuel saturation. If full of fuel, check canister control and hoses. See CHART C3 for diagnosis.
6. MAF Sensor. An output that causes ECM to sense a higher than normal air flow can cause system to go rich. Unplugging MAF sensor will allow ECM to set a fixed value for sensor. Substitute a different MAF sensor if rich condition is rectified while sensor is unplugged.
7. Fuel. Check for leaking fuel pressure regulator diaphragm by checking vacuum line to regulator for raw fuel.
8. TPS. An intermittent TPS output will cause system to go rich, due to a false indication of engine acceleration.
9. EGR. An EGR staying open (especially at idle) will cause the O2 sensor to indicate a rich exhaust, and could result in a Code E045.

Code E045, Oxygen Sensor Circuit (Rich Exhaust Indicated). Scheme 161

CODE E046, POWER STEERING PRESSURE SWITCH CIRCUIT

The power steering pressure switch incorporated as an ECM discrete input signal representing the parasitic load placed on the engine during high power steering demand periods, such as parking. This load may cause engine to stall under high power steering pump pressure conditions, therefore, the ECM compensates by automatically increasing the engine idle speed, via IAC whenever the switch opens and a low voltage is monitored at ECM terminal No. 1D4. This low voltage indicates a high pressure within the power steering system resulting from high demand. Current is also disrupted to the A/C compressor relay so the A/C clutch is disengaged to further reduce engine load.

To set a Code E046, the following conditions must be met

1. Closed power steering switch. E178 indicates "LO" (low voltage potential).
2. Vehicle speed is greater than 50 MPH.
3. Both conditions existing for a time greater than 12.8 seconds. NOTE: Test numbers refer to test numbers on diagnostic chart.

1. Tests the power steering pressure switch for proper operation by using the self diagnostics system. "LO" should be displayed when high power steering pressure loads are created.
2. This step determines whether the fault is in the switch or the circuit. A jumpered switch connector should normally indicate "HI" if the circuit is complete. If so, the power steering pressure switch or connection is faulty.
3. If the display switches to "HI" when circuit No. 495 is grounded, the fault is an open in circuit No. 450.

An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Check for the following conditions

1. Poor Connection or Damaged Harness. Inspect ECM harness connectors for backed out terminals "1D4", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test. If connections and harness check okay, monitor data EI78 (power steering pressure switch) display, while moving related connectors and wiring harness. If failure is induced, reading will change. This will help to isolate location of the malfunction.

Code E046, Power Steering Pressure Switch Circuit. Scheme 162

CODE E047, ECM-BCM DATA

Check for momentary loss of BCM's 7 volts (circuit No. 807), ignition No. 3 (circuit No. 750) and PROM. Reference "B" charts. If Code E047 is set along with any of the following codes set as HISTORY", B334, B335, B336, B337, B552 and B553, see chart on multiple intermittent codes.

CODE E048, MISFIRE DIAGNOSIS

Code E048 will set if following conditions are met

1. TPS is between .8 and 1.07 volts.
2. RPM is between 1100 and 1400.
3. MPH is between 50 and 60.
4. Oxygen sensor cross counts are greater than 20.
5. All of the above for 3 seconds.

Code E048 will set when a problem exists with electrical system, fuel system or a basic engine problem, such as

1. A fuel related problem (such as restricted fuel injector).
2. A problem with ignition system such as bad plug wires, spark plugs or coil pack.
3. Check for other engine related problems such as burned or worn valves, weak valve springs, poor compression, worn camshaft or faulty lifters.

For additional items to check see TROUBLE SHOOTING.

CODE E051, MEM-CAL ERROR

Checks that all pins are fully inserted in socket. If okay, replace PROM, clear memory and recheck. If Code E051 reappears, replace ECM.

CODE E063, E064 & E065, EXHAUST GAS RECIRCULATION FLOW CHECK

Codes E063, E064 and E065 are EGR flow test failures. The ECM, on a closed throttle coast down, will cycle solenoids on and off individually and look for a consequent change in engine RPM and O2 sensor activity.

If a code is set, inspect EGR for damage. Start and idle engine. Enter ECM overrides ES02, ES03 and ES04. You should be able to discern a change in engine RPM as the ECM turns on the EGR. ES02 should result in a small change and ES04 in a large change in RPM. The engine may stall when ES04 is turned on.

Exhaust Gas Recirculation (EGR) Flow Check. Scheme 163

Exhaust Gas Recirculation (EGR) Flow Check. Scheme 164

3.8L 3800 (VIN C) PFI ECM Terminal Identification. Scheme 165

ECM Circuit Schematic A (Part 1 of 3). Scheme 166

ECM Circuit Schematic A (Part 2 of 3). Scheme 167

ECM Circuit Schematic A (Part 3 of 3). Scheme 168

ECM Circuit Schematic B (Part 1 of 4). Scheme 169

ECM Circuit Schematic B (Part 2 of 4). Scheme 170

ECM Circuit Schematic B (Part 3 of 4). Scheme 171

ECM Circuit Schematic B (Part 4 of 4). Scheme 172

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