Engine Controls - Tests W/codes - 2.3L: Diagnosis Oldsmobile Achieva I

SELF-DIAGNOSTIC SYSTEM

Note. Powertrain Control Module (PCM) is also be referred to as Electronic Control Module (ECM) in some diagnostic charts and figures. Terms are used interchangeably.

Control module is equipped with a self-diagnostic system, which detects system failures or abnormalities. When a malfunction occurs, control module will illuminate SERVICE ENGINE SOON light located on instrument panel. SERVICE ENGINE SOON light is also be referred to as the Malfunction Indicator Light (MIL). When malfunction is detected and light is turned on, a corresponding trouble code will be stored in control module memory. To retrieve stored codes, see RETRIEVING CODES (NON-SCAN) . Malfunctions are recorded as hard failures or as intermittent failures.

DIAGNOSTIC PROCEDURE

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

1. Ensure all engine systems not related to computer system are operating properly. DO NOT proceed with testing unless all other problems have been repaired. DIAGNOSTIC CIRCUIT CHECK must be performed before using trouble code charts. See «BASIC TESTING»(ref-19653) article in this section.
2. If trouble codes were displayed (other than Code 12), determine whether codes are hard or intermittent trouble codes. Hard codes will cause SERVICE ENGINE SOON light to glow continuously while engine is running. See HARD OR INTERMITTENT TROUBLE CODE DETERMINATION. For diagnosing hard codes, proceed to appropriate trouble code chart. For diagnosing intermittent codes, proceed to INTERMITTENTS in «TESTS W/O CODES»(ref-19654) article in this section.
3. If no trouble codes are present and a driveability problem exists, refer to SYMPTOMS in «TESTS W/O CODES»(ref-19654) article in this section. Doing so will help identify proper system or component to check in «SYSTEM/COMPONENT TESTS - 2.3L»(ref-19614) article.
4. After necessary repairs are made, clear trouble codes and perform FIELD SERVICE MODE CHECK in «BASIC TESTING»(ref-19653) article in this section.

Note. For information on retrieving codes using a scan tester, refer to user and reference manuals supplied with tester.

READING TROUBLE CODES

Control module stores component failure information under a related trouble code which can be recalled for diagnosis and repair. Trouble codes may be read by counting flashes of SERVICE ENGINE SOON light or by reading digital display on a scan tester. Scan tester is faster to use, more accurate and capable of reading information which otherwise would necessitate testing individual control module and sensor/solenoid connector terminals using a digital voltmeter. See SCAN TESTER USAGE and SCAN DATA .

Note. When using most scan testers, a time delay exists between serial data updates. For instantaneous response, a digital voltmeter must be used.

If scan tester is not available, reading flashes of SERVICE ENGINE SOON light is possible by grounding diagnostic test terminal "B" (if a wire is present) of DLC with ignition on and engine off. see scheme 1 For example, "FLASH, FLASH, pause, FLASH, longer pause" identifies Code 21. First series of flashes is first digit of trouble code. Second series of flashes is second digit of trouble code. Trouble codes are displayed starting with lowest numbered code. Each code is displayed 3 times. Codes will continue to repeat as long as DLC test terminal is grounded.

Note. Trouble codes will be recorded at various operating times. Some codes require operation of that sensor or switch for 5 seconds; others require operation for 5 minutes or longer at normal operating temperature, vehicle speed and load. Therefore, some codes may not set in a service bay operational mode and may require road testing vehicle in order to duplicate condition under which code will set.

TROUBLE CODE DEFINITION

ECM/PCM TROUBLE CODE DEFINITION

Note. Use trouble code charts only if SERVICE ENGINE SOON light is illuminated (indicating a current problem exists).

HARD OR INTERMITTENT TROUBLE CODE DETERMINATION

During any diagnostic procedure, determine if codes are hard failure codes or intermittent failure codes. Diagnostic charts will not usually help analyze intermittent codes. To determine hard codes and intermittent codes

1. Enter diagnostic mode. Read and record all stored trouble codes. Exit diagnostic mode, and clear trouble codes. See «CLEARING TROUBLE CODES»(ref-19584-S18312200652001031200000) .
2. Apply parking brake, and place transmission in Neutral or Park. Block drive wheels, and start engine. SERVICE ENGINE SOON light should go out. Run warm engine at specified curb idle for 2 minutes and note SERVICE ENGINE SOON light.
3. If SERVICE ENGINE SOON light comes on, enter diagnostic mode. Read and record trouble codes. This will reveal hard failure codes. Oxygen sensor related codes may require a road test to reset hard failure after trouble codes were cleared.
4. If SERVICE ENGINE SOON light does not come on, all stored trouble codes were intermittent failures, except as noted above.

CLEARING TROUBLE CODES

Note. On models not utilizing a 12-terminal DLC or if no wire is present in terminal "B", codes are cleared using a scan tester.

Turn ignition switch to ON position, and ground diagnostic test terminal "B" at DLC. see scheme 1 Turn ignition switch to OFF position, and remove control module fuse from fuse block for 10 seconds. Replace fuse. Remove diagnostic terminal ground lead. If fuse cannot be located, pigtail at battery can be disconnected. When power to ECM is remove, degraded driveability may be exhibited until control module "relearns" optimum operational parameters.

Diagnostic Aids

Diagnostic aids (located in many trouble code charts) are additional tips used to help diagnose trouble codes when inspected circuit is okay. Diagnostic aids may help lead to a definitive solution to trouble code problem.

SPECIAL TOOLS (DIAGNOSTIC)

Note. A scan tester plugged into DLC may be used to read trouble codes and check voltages in system on serial data line (terminal "E", or terminal "M"). This can save a great deal of time. For additional information, see SCAN TESTER USAGE and SCAN DATA .

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

Control module will not go into closed loop if code is set. Code may set if vehicle runs out of fuel or stalls while vehicle is in motion. If oxygen sensor ground becomes loose, a false oxygen sensor reading will occur. This can result in a Code 13 being set. On models equipped with an oxygen sensor heating element, element resistance should be 3.5-14 ohms.

CODE 13 PCM TERMINAL & CIRCUIT WIRING IDENTIFICATION

Code 13 Schematic (2.3L) Open Oxygen Sensor Circuit. Scheme 57

Code 13 Flow Chart (2.3L) Open Oxygen Sensor Circuit. Scheme 58

After engine is started, temperature should rise steadily to about 190°F (88°C) and then stabilize when thermostat opens. At normal operating temperature, signal voltage at control module terminal should be 1.5-2.0 volts. Check sensor for shifted calibration by using sensor TEMPERATURE-TO-RESISTANCE VALUES table. When code is set, control module will turn on electric cooling fan(s) if equipped.

CODE 14 PCM TERMINAL & CIRCUIT WIRING IDENTIFICATION

TEMPERATURE-TO-RESISTANCE VALUES (1)

Code 14 Schematic (2.3L) Coolant Temperature Sensor Signal Voltage Low. Scheme 59

Code 14 Flow Chart (2.3L) Coolant Temperature Sensor Signal Voltage Low. Scheme 60

After engine is started, temperature should rise steadily to about 190°F (88°C) and then stabilize when thermostat opens. At normal operating temperature, voltage at control module sensor signal line should be 1.5-2.0 volts. Check sensor for shifted calibration by using sensor TEMPERATURE-TO-RESISTANCE VALUES table. When code is set, control module will turn on electric cooling fan(s) if equipped.

CODE 15 PCM TERMINAL & CIRCUIT WIRING IDENTIFICATION

TEMPERATURE-TO-RESISTANCE VALUES (1)

Code 15 Flow Chart (2.3L) Coolant Temperature Sensor Signal Voltage High. Scheme 61

If vehicle has non-standard electrical equipment (CB radios, 2-way radios, etc.) check to see if their operation may be causing a 7X resync which may set Code 19. If a "cranks but won't start" condition has existed, code may be due to 20 attempted starts without turning off ignition switch.

Code 19 Schematic (2.3L) Intermittent 7X Signal. Scheme 62

Code 19 Flow Chart (2.3L) Intermittent 7X Signal. Scheme 63

A scan tester displays throttle position in volts. Closed throttle voltage should be low. Voltage should increase gradually to about 4.5 volts at a steady rate as throttle angle is increased. If code is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.

Code 21 Schematic (2.3L) Throttle Position Sensor Signal Voltage High. Scheme 64

Code 21 Flow Chart (2.3L) Throttle Position Sensor Signal Voltage High. Scheme 65

CODE 21 PCM TERMINAL & CIRCUIT WIRING IDENTIFICATION

A scan tester displays throttle position in volts. Closed throttle voltage should be low. Voltage should increase gradually to about 4.5 volts at a steady rate as throttle angle is increased. If code is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.

CODE 22 PCM TERMINAL & CIRCUIT WIRING IDENTIFICATION

Code 22 Flow Chart (2.3L) Throttle Position Sensor Signal Voltage Low. Scheme 66

If engine is allowed to cool overnight, coolant and MAT sensor values should be close to each other when measured by scan tester. Code will result if signal and ground circuits become open. Check sensor for shifted calibration by using sensor TEMPERATURE-TO-RESISTANCE VALUES table.

CODE 23 PCM TERMINAL & CIRCUIT WIRING IDENTIFICATION

TEMPERATURE-TO-RESISTANCE VALUES (1)

Code 23 Schematic (2.3L) MAT Sensor Signal Voltage High. Scheme 67

Code 23 Flow Chart (2.3L) MAT Sensor Signal Voltage High. Scheme 68

A faulty or misadjusted park/neutral switch may set a false Code 24. Use scan tester to check for proper signal in Drive while wiggling shifter. Code 24 may set if vehicle is power braked (brakes applied and throttle depressed) for more than 10 seconds.

Code 24 Schematic (2.3L) Vehicle Speed Sensor. Scheme 69

Code 24 Flow Chart (2.3L) Vehicle Speed Sensor. Scheme 70

If engine is allowed to cool overnight, coolant temperature sensor and MAT sensor values should be close to each other when measured by a scan tester. A Code 25 will result if sensor signal circuit is shorted to ground. Check sensor for shifted calibration by using sensor TEMPERATURE-TO-RESISTANCE VALUES table.

CODE 25 PCM TERMINAL & CIRCUIT WIRING IDENTIFICATION

TEMPERATURE-TO-RESISTANCE VALUES (1)

Code 25 Flow Chart (2.3L) MAT Sensor Signal Voltage Low. Scheme 71

Tech 1 and other scan testers have the ability to command the MIL and TEMP light on and off. A faulty driver circuit or poor connection can result in setting of Code 26.

Code 26 Schematic (2.3L) Quad-Driver Error. Scheme 72

Code 26 Flow Chart (2.3L) Quad-Driver Error. Scheme 73

Tech 1 has the ability to command shift solenoids and TCC PWM on and off. A faulty connection or an open circuit can result in setting Code 29.

Code 29 Schematic (2.3L) Quad-Driver 3. Scheme 74

Code 29 Flow Chart (2.3L - 1 Of 2) Quad-Driver 3. Scheme 75

Code 29 Flow Chart (2.3L - 2 Of 2) Quad-Driver 3. Scheme 76

With ignition switch in ON position and engine stopped, manifold pressure is equal to atmospheric pressure and signal voltage will be high. Comparison of BARO readings from a known good vehicle using same sensor is a good way to check accuracy of suspect sensor. Readings should be same within .4 volt. Code 33 will result if ground circuit is open, MAP signal circuit is shorted to voltage or to 5-volt reference circuit.

CODE 33 PCM TERMINAL & CIRCUIT WIRING IDENTIFICATION

Code 33 Schematic (2.3L) MAP Sensor Signal Voltage High. Scheme 77

Code 33 Flow Chart (2.3L) MAP Sensor Signal Voltage High. Scheme 78

With ignition switch in ON position and engine stopped, manifold pressure is equal to atmospheric pressure and signal voltage will be high. Comparing BARO readings with a known good vehicle using same sensor is a good way to check accuracy of suspect sensor. Readings should be same within .4 volt. A Code 34 will also result if 5-volt reference and MAP signal circuits are open or shorted to ground.

CODE 34 PCM TERMINAL & CIRCUIT WIRING IDENTIFICATION

Code 34 Flow Chart (2.3L) MAP Sensor Signal Voltage Low. Scheme 79

A slow, unstable idle may be caused by a system problem which cannot be overcome by IAC. Scan counts will be greater than 60 if idle is too low and zero counts if idle is too high. If idle is too high, stop engine. Fully extend IAC with driver. Start engine. If idle speed is greater than 800 RPM, look for possible vacuum leaks.

Check knock sensor signal circuit for a potential open or short to ground. An open knock signal circuit would cause 5-volt reference to remain high at PCM knock signal terminal. A short to ground in knock signal circuit would cause 5-volt reference signal to pull low to near zero volts. Resistance to ground through knock sensor should be 3300-4500 ohms. Also check for proper installation of MEM-CAL.

Code 43 Schematic (2.3L) ESC Error. Scheme 80

Code 43 Flow Chart (2.3L) ESC Error. Scheme 81

Using scan tester, observe Block Learn Memory (BLM) value at different RPMs. If conditions for a Code 44 exist, block learn value will be about 150.

If other codes of lower number are set with Code 45, use those charts first. Malfunction in MAP or TPS sensor circuits can cause a Code 45 to set. If other codes are not set, Code 45, rich exhaust, is most likely caused by

A plugged fuel filter or restricted fuel line can prevent adequate fuel from being supplied during power enrichment. Vapor lock can also cause Code 55.

Code 55 Schematic (2.3L) Fuel Lean Monitor. Scheme 82

Code 55 Flow Chart (2.3L) Fuel Lean Monitor. Scheme 83

Code 55 Flow Chart. Scheme 84

An open in injector drive or "peak and hold" circuits or PCM drive circuits shorted to voltage will cause a Code 65 to be set and also cause misfire due to an inoperative pair of injectors. "Peak and hold" circuits shorted to ground will cause a Code 65 to set while allowing injectors to pulse. An intermittent problem would have to be present for at least 20 seconds to set Code 65.

Code 65 Schematic (2.3L) Injector Current Low. Scheme 85

Code 65 Flow Chart (2.3L - 1 Of 2) Injector Current Low. Scheme 86

Code 65 Flow Chart (2.3L - 2 Of 2) Injector Current Low. Scheme 87

The 5-volt reference for the TPS is the same 5 volts used by the A/C pressure sensor. If the 5-volt reference has a short to ground, the MAP sensor, A/C pressure sensor and other related sensors will also have a short to ground. This short to ground will not damage the PCM. When the shorted 5-volt reference circuit is repaired, the PCM 5-volt reference will return to normal.

In extremely low temperature climate, the A/C pressure signal can drop as low as .3 volt. If this happens, Code 66 will set and disable the A/C system. Clear code and recheck A/C system in a heated garage to determine if outside ambient temperature is cause for Code 66 setting.

Code 66 Schematic (2.3L) A/C Pressure Sensor. Scheme 88

Code 66 Flow Chart (2.3L) A/C Pressure Sensor. Scheme 89