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

HARD FAILURES

Hard failures cause SERVICE ENGINE SOON light to glow and remain on until malfunction is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) charts. If a sensor fails, control module will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is functional, but it will most likely encounter degraded driveability.

INTERMITTENT FAILURES

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

RETRIEVING CODES (NON-SCAN)

Note. On models using a 12-terminal DLC (previously referred to as the ALDL), if a wire is present at terminal "B", inserting a jumper wire into test and ground terminals of DLC with engine running will cause fuel injected vehicles to enter field service mode. Flashes of SERVICE ENGINE SOON light will not indicate codes if this is done. See FIELD SERVICE MODE CHECK in BASIC TESTING article in the ENGINE PERFORMANCE section. On models not using a 12-terminal DLC or not having a wire present in terminal "B", codes must be retrieved using a hand-held scan tester.

DATA LINK CONNECTOR (DLC) TEST TERMINALS

1. Turn ignition on. DO NOT start engine. SERVICE ENGINE SOON light should glow. Locate DLC attached to control module wiring harness. Most DLC's are located under dash on driver side of vehicle. For exact location of DLC, see COMPONENT LOCATIONS in «SYSTEM/COMPONENT TESTS - 2.3L»(ref-19614) article in this section. Insert jumper wire from terminal "B" (diagnostic test terminal) to terminal "A" (ground) of DLC. (Scheme 90)
2. SERVICE ENGINE SOON light should begin to flash codes. Each code will be repeated 3 times. If codes are not flashed or SERVICE ENGINE SOON light does not glow, perform DIAGNOSTIC CIRCUIT CHECK in «BASIC TESTING»(ref-19653) article in this section. To exit diagnostic mode, turn ignition off and remove jumper wire from DLC connector.

Scheme 90

Field Service Mode Check (If Available)

If DLC test terminal "B" is grounded with engine running, SERVICE ENGINE SOON light will indicate operational mode of engine. This test confirms proper operation of fuel system and verifies "closed loop" operation. Clear codes and perform this test after any repair is completed. Some models require the use of a scan tester to enter field service mode. Field service mode check can be found by proceeding to FIELD SERVICE MODE CHECK in BASIC TESTING article in this section.

SCAN TESTER USAGE

Note. Before connecting scan tester to vehicle, diagnostic system should be checked to determine if system is operating properly and if information received will be accurate. This is done by performing DIAGNOSTIC CIRCUIT CHECK located in the BASIC TESTING article in this section. If vehicle does not pass diagnostic circuit check, information received may be invalid.

Scan tester is a specialized tester which, when plugged into DLC, can be used to diagnose on-board computer control systems by providing instant access to circuit voltage information without need to crawl under dash or hood to backprobe sensors and connectors.

Scan tester cuts down diagnostic time dramatically by furnishing input data (voltage signals) which can be compared to specification parameters. See SCAN DATA . They may also furnish information on output device (solenoids and motors) status. However, status parameters only indicate output signals have been sent to devices by control module; they do not indicate whether devices have responded properly to signal. Verify proper response at output device using a voltmeter or test light.

Vehicles utilizing a 16-terminal DLC or 12-terminal DLC with terminal "B" not used, must use a scan tester for retrieving codes or enter Field Service Mode.

Note. Code 12 should always exist when DLC terminal "B" is grounded with key on and engine not running, but it may not be indicated by all makes of scan testers.

A problem may exist even if trouble codes are not present. About 80 percent of driveability problems occur without trouble codes. Sensors that are out of calibration will not set a trouble code but will cause driveability problems.

Using a scan tester is the easiest method of checking sensor specifications and other data parameters. Tester is also useful in finding intermittent wiring problems by wiggling wiring harnesses and connections (key on, engine off) while observing data parameters. See SCAN DATA.

Note. If erroneous voltage signals are suspected, verify tester information using a digital voltmeter and wiring schematic. If non-existent codes are displayed, turn ignition off, remove tester, turn ignition on and ground DLC test terminal "B". Same codes flashed by SERVICE ENGINE SOON light should be indicated by scan tester.

SCAN DATA

Note. Information contained in following tables is typical of readings taken on vehicle with engine idling, upper radiator hose hot, closed throttle, transmission in Park or Neutral, "closed loop" status achieved and all accessories off (except as noted in tables). Data parameters are updated a minimum of every 1 1/4 seconds. On systems using P-4 computers, parameter updates are more frequent. Not all devices and systems are used on all models; following lists only represent most commonly used parameters. For additional information, refer to owner manual furnished with tester.

MULTIPORT FUEL INJECTION (MFI)

ECM/PCM CODE CHARTS

Note. In following diagnostic tests, schematics and illustrations are courtesy of General Motors Corp.

CODE 13, OPEN OXYGEN SENSOR CIRCUIT

Note. Test numbers refer to numbers on diagnostic chart.

1. This tests if problem still exists. Vehicle cannot enter "closed loop" mode if oxygen sensor circuit is open. Code indicates an open in O2 sensor circuit. Code will set if Engine is at normal operating temperature, neither Code 21 nor Code 22 is stored, oxygen sensor voltage is constant within a specified range (.34-.55 volt), throttle angle is greater than idle, a precalibrated amount of time has elapsed since start-up and all conditions have existed for a precalibrated amount of time.
2. Determines if oxygen sensor, wiring or control module is at fault. If wiring is good, grounding oxygen sensor wire will cause .45 volt reference supplied by control module to pull low.
3. This tests oxygen sensor circuit wiring. Use only a high impedance (10-megohm minimum) digital voltmeter.

CODE 14, COOLANT TEMPERATURE SENSOR SIGNAL VOLTAGE LOW

1. For shared sensor ground tie-offs, see appropriate diagram in «WIRING DIAGRAMS»(ref-19584-S23469361122001031200000) section. NOTE: This chart assumes engine cooling system is functioning properly (not overheating). Test numbers refer to numbers on diagnostic chart.

1. Code indicates control module has seen low coolant sensor voltage signal (high temperature) at control module terminal for a precalibrated period of time. This checks if conditions for code still exist.
2. This tests for grounded sensor signal line between control module and coolant sensor.

CODE 15, COOLANT TEMPERATURE SENSOR SIGNAL VOLTAGE HIGH

1. For shared sensor ground tie-offs, see appropriate diagram in «WIRING DIAGRAMS»(ref-19584-S23469361122001031200000) section. NOTE: Test numbers refer to numbers on diagnostic chart.

1. Code indicates control module has seen high resistance in coolant sensor circuit. This could be due to high resistance (cold temperature) or high voltage at coolant sensor terminal at control module for a precalibrated period of time. This checks if conditions for code still exist.
2. This test simulates a low voltage condition. If control module recognizes low voltage signal, scan tester will display greater than 130°C. This indicates control module and wiring are not at fault.
3. This test determines if coolant sensor ground or signal circuit is open.

CODE 19, INTERMITTENT 7X SIGNAL

The ignition control module sends a reference signal to the PCM 7 times per crankshaft revolution to indicate crankshaft position and RPM so that the PCM can determine when to pulse the ignition coils and control ignition timing. A 5-volt reference is supplied to the PCM from terminal "G" of the ignition module. This 5-volt reference signal is monitored by the PCM. The ignition module pulls this signal low based upon 7X reference pulses. The seventh pulse is used for crankshaft position (sync) reference. Code 19 is set if the PCM misses at least 20 sync pulses within 4 minutes and 16 seconds.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step determines if the PCM recognizes a problem. If it doesn't set Code 19 at this point, the problem is intermittent.
2. When a 7X resync occurs, engine stumble also occurs. If a component connection or circuitry is at fault, engine stumble may be induced by wiggling the circuit or connection.

CODE 21, THROTTLE POSITION SENSOR SIGNAL VOLTAGE HIGH

1. For shared sensor ground tie-offs, see appropriate diagram in «WIRING DIAGRAMS»(ref-19584-S23469361122001031200000) section. NOTE: Test numbers refer to numbers on diagnostic chart.

1. This test checks if code is result of a hard failure or an intermittent condition.
2. This test simulates a low-voltage condition. If control module recognizes change of state, control module and wiring are okay.
3. This step isolates a faulty sensor, control module or open sensor ground circuit. If sensor ground is shared by another sensor, an accompanying code related to that sensor may exist.

CODE 22, THROTTLE POSITION SENSOR SIGNAL VOLTAGE LOW

1. For shared sensor ground tie-offs, see appropriate diagram in «WIRING DIAGRAMS»(ref-19584-S23469361122001031200000) section. NOTE: Test numbers refer to numbers on diagnostic chart.

1. This test checks if code is result of a hard failure or an intermittent condition.
2. This test simulates conditions for setting code. If control module recognizes change of state, control module and wiring are okay.
3. This simulates a high signal voltage to check for an open in TPS signal line to control module. Scan tester should recognize this signal and display high TPS voltage.

CODE 23, MAT SENSOR SIGNAL VOLTAGE HIGH

1. For shared sensor ground tie-offs, see appropriate diagram in «WIRING DIAGRAMS»(ref-19584-S23469361122001031200000) section. NOTE: Test numbers refer to numbers on diagnostic chart.

1. This checks if code is result of a hard failure or an intermittent condition. Code will set if engine has been running for a precalibrated period of time, has reached operating temperature and signal voltage indicates a intake air temperature less than -22°F (-30°C).
2. This simulates conditions for setting code. If scan tester displays a high temperature, control module and wiring are not at fault.
3. This checks for continuity of sensor signal and ground circuits. If ground circuit is shared by other sensors and ground circuit is open, accompanying codes related to those sensors may be present.

CODE 24, VEHICLE SPEED SENSOR

Speed sensor, which is a Permanent Magnet (PM) generator, provides control module with vehicle speed information. PM generator, mounted in transmission, produces a pulsing AC voltage signal whenever vehicle speed is greater than 2 MPH. Voltage level and pulses increase with vehicle speed. Control module converts pulsing voltage to MPH, which is used by control module to calculate vehicle adjustments.

Note. Test numbers refer to numbers on diagnostic chart.

1. Code 24 sets when MPH reads zero, transmission is not in Park or Neutral, engine speed indicates vehicle is in a cruise mode (1200-4400) RPM, TPS indicates closed throttle and MAP sensor senses high manifold vacuum. All of these conditions must be met for 2-5 seconds. PM generator only produces a voltage signal if drive wheels are turning greater than 2 MPH.
2. Before replacing control module, PROM/MEM-CAL should be checked for correct application.

CODE 25, MAT SENSOR SIGNAL VOLTAGE LOW

1. For shared sensor ground tie-offs, see appropriate diagram in «WIRING DIAGRAMS»(ref-19584-S23469361122001031200000) section. NOTE: Test numbers refer to numbers on diagnostic chart.

1. This checks if code is hard failure or intermittent condition. Code 25 will set if a MAT temperature greater than 266°F (130°C) is sensed for more than a precalibrated period.
2. This simulates condition for Code 23. If control module recognizes open circuit and scan tester displays temperature of less than -30°C, control module and wiring are okay.

CODE 26, QUAD-DRIVER ERROR

PCM controls most components with electronic switches completing a ground circuit when actuated. Switches are arranged in groups of 4, called Quad-Driver Modules (QDMs), which can independently control up to 4 outputs (control module terminals). When an output is actuated, terminal is grounded and its voltage normally will be low. When an output is off, its terminal voltage will normally be high.

QDMs are fault-protected. If a relay or solenoid coil is shorted (having very low resistance) or if control side of circuit is shorted to voltage, too much current would be allowed into QDM. QDM senses this and turns driver off or QDM's internal resistance increases to limit current flow and protect QDM. Result is high output terminal voltage when it should be low. If circuit from battery voltage or component is open or control side of circuit is shorted to ground, terminal voltage will be low, even when output is turned off. Either of these conditions is considered to be a QDM fault.

Each QDM has a separate fault line to indicate presence of a current fault to control module central processor. A scan tester displays status of each of these fault lines as "low equals okay" or "high equals fault".

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks to see if code was set as the result of a current or intermittent condition.
2. Checks MIL operation.
3. Checks TEMP light.

CODE 27, QUAD-DRIVER NO. 1 ERROR

PCM controls most components with electronic switches completing a ground circuit when actuated. Switches are arranged in groups of 4, called Quad-Driver Modules (QDMs), which can independently control up to 4 outputs (control module terminals). When an output is actuated, terminal is grounded and its voltage normally will be low. When an output is off, its terminal voltage will normally be high.

QDMs are fault-protected. If a relay or solenoid coil is shorted (having very low resistance) or if control side of circuit is shorted to voltage, too much current would be allowed into QDM. QDM senses this and turns driver off or QDM's internal resistance increases to limit current flow and protect QDM. Result is high output terminal voltage when it should be low. If circuit from battery voltage or component is open or control side of circuit is shorted to ground, terminal voltage will be low, even when output is turned off. Either of these conditions is considered to be a QDM fault.

Each QDM has a separate fault line to indicate presence of a current fault to control module central processor. A scan tester displays status of each of these fault lines as "low equals okay" or "high equals fault". Because of the brake and 3rd gear switches in the TCC circuit, Code 27 will set if QDM No. 1 is high for 20 seconds or more with battery voltage is sensed at greater than 10.5 volts and TCC is commanded on.

Code 27 Schematic (2.3L) Quad-Driver No. 1 Error. Scheme 91

Code 27 Flow Chart (2.3L) Quad-Driver No. 1 Error. Scheme 92

CODE 28, QUAD-DRIVER NO. 2 ERROR

PCM controls most components with electronic switches completing a ground circuit when actuated. Switches are arranged in groups of 4, called Quad-Driver Modules (QDMs), which can independently control up to 4 outputs (control module terminals). When an output is actuated, terminal is grounded and its voltage normally will be low. When an output is off, its terminal voltage will normally be high.

QDMs are fault-protected. If a relay or solenoid coil is shorted (having very low resistance) or if control side of circuit is shorted to voltage, too much current would be allowed into QDM. QDM senses this and turns driver off or QDM's internal resistance increases to limit current flow and protect QDM. Result is high output terminal voltage when it should be low. If circuit from battery voltage or component is open or control side of circuit is shorted to ground, terminal voltage will be low, even when output is turned off. Either of these conditions is considered to be a QDM fault.

Each QDM has a separate fault line to indicate presence of a current fault to control module central processor. A scan tester displays status of each of these fault lines as "low equals okay" or "high equals fault". Code 28 will set if QDM No. 2 is high for 20 seconds or more with battery voltage is sensed at greater than 10.5 volts.

Code 28 Schematic (2.3L) Quad-Driver No. 2 Error. Scheme 93

Code 28 Flow Chart (2.3L) Quad-Driver No. 2 Error. Scheme 94

CODE 29, QUAD-DRIVER 3

PCM controls most components with electronic switches completing a ground circuit when actuated. Switches are arranged in groups of 4, called Quad-Driver Modules (QDMs), which can independently control up to 4 outputs (control module terminals). When an output is actuated, terminal is grounded and its voltage normally will be low. When an output is off, its terminal voltage will normally be high.

QDMs are fault-protected. If a relay or solenoid coil is shorted (having very low resistance) or if control side of circuit is shorted to voltage, too much current would be allowed into QDM. QDM senses this and turns driver off or QDM's internal resistance increases to limit current flow and protect QDM. Result is high output terminal voltage when it should be low. If circuit from battery voltage or component is open or control side of circuit is shorted to ground, terminal voltage will be low, even when output is turned off. Either of these conditions is considered to be a QDM fault.

Each QDM has a separate fault line to indicate presence of a current fault to control module central processor. A scan tester displays status of each of these fault lines as "low equals okay" or "high equals fault". Code 29 will set if QDM No. 2 is high for 20 seconds or more with battery voltage is sensed at greater than 10.5 volts.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks if PCM is grounding shift solenoids "A" and "B".
2. Checks to see if Tech-1 can command shift solenoids.
3. Checks for short to voltage on shift solenoid circuits.
4. Checks continuity of shift solenoid circuits.
5. Checks to see if PCM is grounding TCC PWM.
6. Checks to see if PCM can command TCC PWM.

CODE 33, MAP SENSOR SIGNAL VOLTAGE HIGH

1. For shared sensor reference and shared sensor ground tie -offs, see appropriate diagram in «WIRING DIAGRAMS»(ref-19584-S23469361122001031200000) section. NOTE: Test numbers refer to numbers on diagnostic chart.

1. This test confirms Code 33 and determines if it is result of a hard failure or an intermittent condition. Code 33 will set when voltage signal reading is too high for greater than a precalibrated period of time, TPS voltage indicates throttle is closed and neither Code 21 nor 22 is present.
2. This step simulates conditions for a Code 34. If control module recognizes and sets Code 34, low MAP signal, control module and 5-volt reference and MAP signal circuits are not at fault. If ground circuit is shared with other sensors and ground circuit becomes open, additional codes related to these sensors may be set.

CODE 34, MAP SENSOR SIGNAL VOLTAGE LOW

1. For shared sensor reference and shared sensor ground tie -offs, see appropriate diagram in «WIRING DIAGRAMS»(ref-19584-S23469361122001031200000) section. NOTE: Test numbers refer to numbers on diagnostic chart.

1. This confirms Code 34 and determines if code was caused by a hard failure or an intermittent fault. Code 34 will set when ignition is on and MAP signal voltage is low. On some systems, engine must be running to set code.
2. Jumpering MAP signal to 5-volt reference at MAP harness connector will determine if sensor is at fault or if a problem exists with control module or wiring.
3. Scan tester may not display 12 volts. Control module recognizes voltage as greater than 4 volts (high MAP voltage signal), indicating control module and MAP signal circuit are not at fault.

CODE 35, IAC IDLE SPEED ERROR

Code 35 will set when closed throttle engine speed is 150 RPM greater or less than correct idle speed for 20 seconds.

Note. Test numbers refer to numbers on diagnostic chart.

1. Tech 1 RPM control mode is used to extend and retract IAC valve. Movement is verified by an engine speed change. If no change in speed occurs, valve can be retested when removed from throttle body. If IAC valve is retracted beyond control range (about 1500 RPM), many flashes in extend position may occur before engine speed begins to drop. This is normal on certain engines. Fully extending IAC may cause engine to stall. This may be normal.
2. This test uses Tech 1 to command IAC-controlled idle speed. Control module issues commands to obtain requested idle speed. Each light on node light should flash Red and Green while IAC valve is cycled. While sequence of color is not important, check circuits for faults beginning with poor terminal contacts if either light is off or does not flash Red and Green.

System Too Lean

If air/fuel ratio is too lean, idle speed may be either too high (check for vacuum leaks) or too low. Engine speed may vary up and down; disconnecting IAC may not help. Scan and/or digital voltmeter (10-megohm) will read an oxygen (O2) sensor output less than 300 mV (.3 volt). Check for low fuel pressure or water in fuel. A contaminated O2 sensor (caused by silicone) will produce lean air/fuel mixtures with an O2 sensor output fixed greater than 800 mV (.8 volt). This may also set Code 45.

System Too Rich

If air/fuel ratio is too rich, idle speed will be too low and scan tester counts will usually be greater than 80. System may be obviously rich, with Black smoke from exhaust pipe. Scan tester and/or voltmeter will read an O2 sensor voltage signal fixed greater than 800 mV (.8 volt). Look for high fuel pressure and injectors leaking or sticking. Remove IAC, and inspect bore for foreign material and evidence of IAC valve dragging bore.

Throttle Body

Remove IAC, and inspect bore for evidence of IAC valve dragging.

IAC Valve Connections

Inspect carefully for loose or corroded connections.

PCV Valve

An incorrect PCV valve may cause incorrect idle speed.

Code 35 Schematic (2.3L) IAC Idle Speed Error. Scheme 95

Code 35 Flow Chart (2.3L) IAC Idle Speed Error. Scheme 96

CODE 43, ESC ERROR

Note. Test numbers refer to numbers on diagnostic chart. If an audible knock is heard from engine at idle, repair internal engine problems before proceeding.

1. If tapping on engine does not produce a knock signal on scan tester, try tapping engine closer to sensor before proceeding.
2. PCM supplies a 5-volt reference signal on knock sensor line. With knock sensor connected, this signal is pulled low to about 2.5 volts. Knock signal, which is an AC signal, rides on this 2.5-volt DC signal.
3. This test determines if knock sensor is faulty or if ESC portion of MEM-CAL is faulty.

CODE 44, LEAN EXHAUST INDICATION

Note. Some models engines are equipped with 2 oxygen sensors. On these models, Code 44 will set if the left sensor circuit is lean. Code 64 will set if the right sensor circuit is lean. Use this chart for Code 64 also and perform tests for applicable sensor.

O2 sensor acts like an open sensor circuit and produces no voltage when exhaust temperature is less than 600°F (316°C). An open sensor circuit or cold sensor causes "open loop" operation. On models with 2 oxygen sensors, Code 44 will reflect a lean left O2 sensor; Code 64 will indicate a lean right O2 sensor. Perform test procedures for right or left sensor as necessary.

Note. Test number refers to number on diagnostic chart.

1. Checks to see if O2 sensor is registering a lean condition. Code 44 is set when O2 sensor voltage signal at control module is low (less than .3 volt) for a precalibrated period and system is operating in "closed loop".

O2 Sensor Wire

O2 sensor wire may be mispositioned and laying against exhaust manifold. Check for ground between sensor and wire connector.

Fuel Contamination

Water, even small amounts, near in-tank fuel pump inlet can be delivered to injector. Water may cause a lean exhaust and set Code 44.

Fuel Pressure

System will be lean if fuel pressure is low. If necessary, monitor fuel pressure while driving vehicle. For fuel pressure checking procedure, see BASIC TESTING article in this section.

Exhaust Leaks

If exhaust system has large leaks, exhaust system negative pressure pulses can cause outside air to be drawn into system and past O2 sensor. Vacuum or crankcase leaks can also cause a lean condition. Misfire Or Stall

If engine misfires or stalls (including running out of fuel) while vehicle is moving, a Code 44 may set. If Code 44 is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.

CODE 44 PCM TERMINAL & CIRCUIT WIRING IDENTIFICATION

Code 44 Flow Chart (2.3L) Lean Exhaust Indication. Scheme 97

Code 44 Flow Chart. Scheme 98

CODE 45, RICH EXHAUST INDICATION

Note. On some models engines are equipped with 2 oxygen sensors. On these models, Code 45 will set if the left sensor circuit is rich. Code 65 will set if the right sensor circuit is lean. Use this chart for Code 65 also and perform tests for applicable sensor.

O2 sensor acts like an open sensor circuit and produces no voltage when exhaust temperature is less than 600°F (316°C). An open sensor circuit or cold sensor causes "open loop" operation.

Code 45 indicates a rich exhaust. Diagnosis should begin with fuel pressure, leaking injector, HEI shielding (ground), vapor canister fuel saturation, coolant sensor, MAP sensor, O2 sensor contamination and TPS intermittent output.

On models using 2 oxygen sensors, Code 45 will reflect a rich left O2 sensor; Code 65 will indicate a rich right O2 sensor. Perform test procedures for right or left sensor as necessary.

Note. Test number refers to number on diagnostic chart.

1. Test checks to see if O2 sensor is registering a rich condition. Code 45 is set when vehicle is at operating temperature (in "closed loop"), throttle angle is greater than idle, O2 sensor signal at control module is greater than .7 volt for a precalibrated period and time since engine start is one minute or more.

Fuel Pressure High

If fuel pressure is too high, air/fuel ratio will be rich. For fuel pressure checking procedure, see BASIC TESTING article in this section. Control module can compensate for slight increases, but a Code 45 will be set if air/fuel ratio becomes too rich.

Ignition Ground

If an open occurs on HEI ground circuit, HEI induced electrical "noise" may result, causing simulated reference pulses to be picked up by control module on reference line of EST harness. Additional pulses result in a higher than actual engine speed signal. Control module will increase injector pulse width ("on" time) to match increased RPM signal. Scan tester will show higher than actual RPM, which can help in diagnosing this problem.

Evaporative Fuel Canister

Fuel saturation of charcoal canister will cause a rich air/fuel ratio. If canister is full of fuel, check canister control valves and hoses.

MAP Sensor

An output causing control module to sense a higher than normal manifold pressure (low vacuum) can cause system to go rich. Disconnecting MAP sensor will allow control module to substitute a fixed value for MAP sensor. If condition disappears, substitute a different MAP sensor, and continue testing.

TPS

An intermittent TPS output will cause system to operate rich due to a false indication of engine acceleration.

O2 Sensor Contamination

O2 sensor contamination, caused by silicone in certain fuels or use of improper RTV sealant, may cause a White powdery coating to cover exterior of O2 sensor. False high signal voltage (low oxygen content sensed) produced is interpreted by control module as a rich mixture, causing control module to set Code 45.

EGR Problem

EGR valve sticking open at idle is usually accompanied by a rough idle and/or stalling. Also check for shorted or leaking injector and fuel-contaminated oil. If Code 45 is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.

CODE 45 PCM TERMINAL & CIRCUIT WIRING IDENTIFICATION

Code 45 Flow Chart (2.3L) Rich Exhaust Indication. Scheme 99

CODE 51, FAULTY PROM/MEM-CAL

Ensure all pins are fully inserted in socket. If pins are okay, replace PROM/MEM-CAL, clear memory and recheck. If Code 51 reappears, replace control module.

CODE 52, FAULTY CAL-PAK

Ensure all pins are fully inserted in socket. If pins are okay, replace CAL-PAK, clear memory and recheck. If Code 51 reappears, replace control module.

CODE 53, SYSTEM VOLTAGE HIGH

This code indicates a basic charging system problem. Code 53 will set when voltage at control module terminal is greater or less than specification for a precalibrated time. If voltage at PCM battery voltage terminal is not within specification, check and repair charging system.

CHARGING SYSTEM SPECIFICATIONS

Code 53 Flow Chart (2.3L) System Voltage High. Scheme 100

CODE 55, PCM ERROR

Ensure PCM grounds are okay. Ensure correct EPROM is being used and that it is properly installed. If okay, replace PCM. Clear codes, confirm closed loop operation and check operation of Malfunction Indicator Light (MIL).

CODE 55, FUEL LEAN MONITOR

PCM is capable of determining if fuel system can deliver adequate fuel during power enrichment (heavy acceleration). During power enrichment conditions, PCM expects to see both O2 sensors registering rich. If both sensors do not register rich, Code 55 will set.

Note. Test numbers refer to numbers on diagnostic chart.

1. Code 55 will set if PCM detects lean O2 sensor voltage for 8 seconds during power enrichment. This checks for proper fuel pressure.
2. Restricting the fuel line allows fuel pressure to build to greater than regulated pressure (greater than 47 psi). DO NOT allow pressure to exceed 60 psi.

CODE 65, INJECTOR CURRENT LOW

PCM has 2 injector driver circuits, each controlling a pair of injectors (1 and 4 or 2 and 3). PCM monitors current of each injector driver circuit by measuring voltage drop through a fixed resistor. PCM is able to control voltage drop. Current through each driver is allowed to rise to peak of 4 amps, enabling injectors to open quickly; current is then reduced to one amp, holding injectors open. This is called "peak and hold". If current cannot reach a 4-amp peak, Code 65 is set. This code is also set if an injector driver circuit is shorted to voltage.

Note. Test numbers refer to numbers on diagnostic chart.

1. Following conditions must be present to set Code 65: 4-amp injector current was not reached on each circuit. Battery voltage greater than 9 volts. Injectors pulsed on longer than calibrated pulse width. Above conditions met for 20 seconds.
2. Checks PCM and harness wiring to 3-terminal injector harness connector.
3. This tests for open injector harness or injector.
4. Results of step 2) will determine which branch to follow on Code 65 flow chart (2 of 2).
5. Each harness was confirmed as being okay in steps 2) and 3). This test will check remainder of circuit from injectors to PCM. NOTE: Although shorted harness or injector (zero ohms) will not set a Code 65, problem should be corrected if discovered.
6. Identifies cause of high resistance found in step 3). A short or low resistance will not cause Code 65 but should be corrected.
7. This tests for grounded "peak and hold" jumpers. This condition would allow injectors to pulse, but it would not allow "peak and hold" operation as current would not flow through resistor in PCM.
8. This checks for short to voltage in injector driver circuits.
9. Determines if injector driver circuits are shorted to ground.
10. This checks output at PCM to determine if injector driver circuits are okay.
11. Checks for proper continuity of "peak and hold" jumpers circuits.

CODE 66, A/C PRESSURE SENSOR

A/C pressure sensor responds to changes in A/C refrigerant system high side pressure. PCM uses A/C compressor load input to determine engine idle speed. Sensor uses a 5-volt reference signal from PCM and returns an input signal to PCM on a separate line. Low pressure (zero psi) will return a signal of about .1 volt. High pressure will return a signal of about 4.9 volts. The PCM will disable the compressor clutch if Code 66 is current.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks voltage signal from A/C pressure sensor to PCM.
2. Checks to see if high signal is from a shorted sensor or a short to voltage in circuit. Normally, disconnecting sensor would make a normal circuit go to nearly zero volts.
3. Checks to see if low voltage signal is from sensor or circuit. Jumpering sensor signal circuit to 5-volt reference checks circuit, connections and PCM.
4. Checks to see if low voltage signal was due to an open in sensor circuit or 5-volt reference circuit; previous step eliminated pressure sensor as a possible cause.

SUMMARY

If no hard fault codes are present, driveability symptoms exist or intermittent codes exist, proceed to TESTS W/O CODES article in this section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.

2.3L (VIN A, D & 3) PCM Wiring Diagram (1 Of 3). Scheme 101

2.3L (VIN A, D & 3) PCM Wiring Diagram (2 Of 3). Scheme 102

2.3L (VIN A, D & 3) PCM Wiring Diagram (3 Of 3). Scheme 103