Engine Controls - Tests W/codes - 3.8L: Diagnosis Oldsmobile Ninety-Eight XI

SELF-DIAGNOSTIC SYSTEM

Note. Electronic Control Module (ECM) may also be referred to as Powertrain Control Module (PCM) 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 may 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 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»(ref-19513-S14053160122001010200000) . For diagnosing hard codes, proceed to appropriate trouble code chart. For diagnosing intermittent codes, proceed to INTERMITTENTS in BASIC TESTING article in this section. Exceptions are Code 13, 15, 24, 44 and 45 charts, which may be used to help diagnose intermittent codes.
3. If no trouble codes were displayed and a driveability problem exists, refer to SYMPTOMS in TESTS W/O CODES article in this section. Doing so will identify proper system or component to check in I - SYS/COMP TESTS article in this section.
4. After necessary repairs are made, clear trouble codes and perform FIELD SERVICE MODE CHECK in BASIC TESTING article in this section.

Note. For information on retrieving codes using a scan tester, refer to user and reference manuals supplied with tester. On Riviera, codes can also be retrieved through Electronic Climate Control Panel (ECCP). For additional information on Riviera ECCP function, see G - PCM/BCM TESTS W/CODES article in this section.

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" of ALDL 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 ALDL 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). Exceptions are Code 13, 15, 24, 44 and 45 charts, which may be used to help diagnose intermittent codes. Anytime control module-related Codes 51, 52 or 55 are displayed with another code, start with 50-series code, and then proceed to lower numbered codes.

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. Manually enter diagnostic mode. Read and record all stored trouble codes. Exit diagnostic mode, and clear trouble codes. See «CLEARING TROUBLE CODES»(ref-19513-S37547123282001010200000) .
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, manually enter diagnostic mode. Read and record trouble codes. This will reveal hard failure codes. Codes 13, 15, 24, 44 and 45 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

Turn ignition switch to ON position, and ground diagnostic test terminal "B" at ALDL connector. 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 removed, 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 ALDL may be used to read trouble codes and check voltages in system on serial data line (terminal "E", or terminal "M" on P-4 systems). 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 13 is set. Code 13 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 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION

Code 13 Schematic (All Models) Open Oxygen Sensor Circuit. Scheme 154

Code 13 Flow Chart (All Models) Open Oxygen Sensor Circuit. Scheme 155

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 14 is set, control module will turn on electric cooling fan(s) if equipped.

CODE 14 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION

TEMPERATURE-TO-RESISTANCE VALUES (1)

Code 14 Schematic (Signal Voltage Low) Coolant Temperature Sensor. Scheme 156

Code 14 Flow Chart (Signal Voltage Low) Coolant Temperature Sensor. Scheme 157

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 14 is set, control module will turn on electric cooling fan(s) if equipped.

CODE 15 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION

TEMPERATURE-TO-RESISTANCE VALUES (1)

Code 15 Flow Chart (Signal Voltage High) Coolant Temperature Sensor. Scheme 158

Check for poor connections or damaged harness. Also, check for an intermittent condition by starting engine and wiggling connection while monitoring battery voltage on scan tester. If voltage status changes abruptly or engine stalls, check for loose connections.

Note. When Code 16 sets, transaxle will be forced to 3rd gear, preventing erratic shifting due to improper voltage.

Code 16 Flow Chart (3.8L) System Voltage High/Low. Scheme 159

An intermittent may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside insulation. Also, check for backed-out connector terminals or broken insulation spark reference circuit. If everything checks okay, try wiggling related wiring harness and connectors while engine is idling. This may help to isolate location of malfunction.

Code 17 Schematic (3.8L (VIN L) "C" & "H" Bodies) RPM Signal Problem. Scheme 160

Code 17 Schematic (3.8L (VIN 1) "C" & "H" Bodies) RPM Signal Problem. Scheme 161

Code 17 Schematic (3.8L "E" Body) RPM Signal Problem. Scheme 162

Code 17 Schematic (3.8L "W" Body) RPM Signal Problem. Scheme 163

Code 17 Flow Chart (3.8L) RPM Signal Problem. Scheme 164

Code 18 indicates an intermittent fault and may not set immediately or under all conditions. Symptoms experienced may help isolate cause of condition. A poor connection or fault in any cam sensor circuit or a faulty cam sensor may cause PCM to re-initialize injector sequence, causing a possible stumble or miss. A poor connection or fault in any crank sensor circuit or fuel control circuit or bent or missing vanes on harmonic balancer interrupter rings will cause PCM to stop pulsing injectors when fault occurs. This will cause an intermittent stumble or stall.

Code 18 Flow Chart (3.8L "C", "H" & "W" Bodies) CAM/CRANK Error. Scheme 165

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 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION

Code 21 Schematic (All Models) Throttle Position Sensor (Signal Voltage High). Scheme 166

Code 21 Flow Chart (All Models) Throttle Position Sensor (Signal Voltage High). Scheme 167

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 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION

Code 22 Flow Chart (All Models) Throttle Position Sensor (Signal Voltage Low). Scheme 168

If engine is allowed to cool overnight, coolant and MAT sensor values should be close to each other when measured by scan tester. Code 23 will result if signal and ground circuits become open. Check sensor for shifted calibration by using sensor TEMPERATURE-TO-RESISTANCE VALUES table.

CODE 23 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION

TEMPERATURE-TO-RESISTANCE VALUES (1)

Code 23 Schematic MAT Sensor (Signal Voltage High). Scheme 169

Code 23 Flow Chart MAT Sensor (Signal Voltage High). Scheme 170

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 (3.8L "W" Body) Vehicle Speed Sensor. Scheme 171

Code 24 Flow Chart (3.8L "W" Body) Vehicle Speed Sensor. Scheme 172

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 ECM TERMINAL & CIRCUIT WIRING IDENTIFICATION

TEMPERATURE-TO-RESISTANCE VALUES (1)

Code 25 Flow Chart MAT Sensor (Signal Voltage Low). Scheme 173

Monitor voltage at each terminal while wiggling related harness connectors, including PCM harness. If the failure is induced, voltage will change. If no faults are found and code resets for no apparent reason, replace PCM.

Code 26 Flow Chart (3.8L "C" & "H" BODIES) (2 of 3) Quad-Driver "A" Error. Scheme 174

Monitor voltage at each terminal while wiggling related harness connectors, including PCM harness. If the failure is induced, voltage will change. If no faults are found and code resets for no apparent reason, replace PCM.

Code 26 Flow Chart (3.8L "E" Body)(2 of 3) Quad-Driver Error. Scheme 175

Monitor voltage at each terminal while wiggling related harness connectors, including PCM harness. If the failure is induced, voltage will change. If no faults are found and code resets for no apparent reason, replace PCM.

Code 26 Flow Chart (3.8L "W" Body) (2 of 4) Quad-Driver "A" Error. Scheme 176

Monitor voltage at each terminal while wiggling related harness connectors, including PCM harness. If the failure is induced, voltage will change. If no faults are found and code resets for no apparent reason, replace PCM.

Code 26 Flow Chart (3.8L "W" Body) (3 of 4) Quad-Driver "A" Error. Scheme 177

MAF sensor produces a frequency signal, which cannot be easily measured. Check for following

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 using driver. Start engine. If idle speed is greater than 800 RPM, look for possible vacuum leaks.

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.

When Code 36 is set, transaxle will be forced into 3rd gear. If code sets due to a grounded circuit No. 1223, only 1st and 2nd gear operation will be available. If circuit No. 1223 is open, only 3rd and 4th gear operation will be available. If fault goes away, normal operation will be resumed for duration of key cycle.

Code 36 Schematic (3.8L "E" Body) Shift Problem. Scheme 178

Code 36 Schematic (3.8L "W" Body) Shift Problem. Scheme 179

Code 36 Flow Chart (3.8L "E" & "W" Bodies) Shift Problem. Scheme 180

A Code 38 in conjunction with a Code 39 or 26 would mean a problem with one or more of following components

Scheme 181

Scheme 182

Scheme 183

Scheme 184

1. Fuse or power supply circuit, brake switch or wire before splice.
2. Code 38 alone is result of a wire or circuit problem between splice and control module, poor connection to control module, or possibly control module itself. If brake switch has failed in an open state, TCC will not engage. Code 38 does not turn on SERVICE ENGINE SOON light on all models. (Scheme 181): Code 38 Schematic (3.8L "C" & "H" Bodies) Brake Switch (Scheme 182): Code 38 Schematic (3.8L "E" Body) Brake Switch (Scheme 183): Code 38 Schematic (3.8L "W" Body) Brake Switch (Scheme 184): Code 38 Flow Chart Brake Switch

A Code 39 in conjunction with a Code 38 would mean a problem with one or more of following components

1. Fuse or power circuit, brake switch or wire before splice.

Code 39 alone indicates a problem at

Scheme 185

Scheme 186

Scheme 187

1. Brake input circuit between splice and TCC solenoid.
2. TCC drive circuit between TCC solenoid and ECM.
3. Poor connection to ECM or ECM itself. (Scheme 185): Code 39 Schematic W/O Tech 1 (3.8L "C & H" Body W/4T60) TCC Circuit (Scheme 186): Code 39 Schematic W/O Tech 1 (3.8L "W" Body W/4T60) TCC Circuit (Scheme 187): Code 39 Flow Chart W/O Tech 1 (3.8L W/4T60 Trans.) TCC Circuit

A Code 39 in conjunction with a Code 38 would mean a problem with one or more of following components

1. Fuse or power circuit, brake switch or wire before splice.

Code 39 alone indicates a problem at

Scheme 188

1. Brake input circuit between splice and TCC solenoid.
2. TCC drive circuit between TCC solenoid and ECM.
3. Poor connection to ECM or ECM itself. see scheme 67: Code 39 Schematic Using Tech 1 (3.8L "C & H" Body W/4T60) TCC Circuit see scheme 68: Code 39 Schematic Using Tech 1 (3.8L "W" Body W/4T60) TCC Circuit (Scheme 188): Code 39 Flow Chart Using Tech 1 (3.8L W/4T60 Trans.) TCC Circuit

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

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

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

If connections and harness are okay, connect a digital volt-ohmmeter between affected terminal to ground, and monitor meter while moving related connectors and wiring harness. If failure is induced, voltage reading will change.

Code 42 Flow Chart - EST Circuit Open Or Grounded. Scheme 189

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 ECM 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 W/O ESC Module (All Models) ESC Error. Scheme 190

Code 43 Flow Chart W/O ESC Module (All Models) ESC Error. Scheme 191

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

CODE 48 - MISFIRE DIAGNOSIS

Note. If multiple codes are present, go to lowest code first. Repairing Code 13, 44 or 45 may correct Code 48.

Code 48 will set if TPS is .48-1.30 volts, RPM is 1300-2100, MPH is 50-60, O2 sensor cross counts are greater than 21 and all of these conditions are met for 30 seconds.

Check for poor harness connections or harness damage. If no problems are found, turn ignition on. Backprobe applicable PCM terminals with a DVOM while wiggling harness. If a failure is induced, voltage reading will change. If no problems are found, check EGR valve pintles and orifices for excessive carbon build-up. Also, check for plugged EGR tube or passages.

Code 53, 54 & 55 Schematic (3.8L (VIN L) "C" & "H" Body) EGR Fault. Scheme 192

Code 53, 54 & 55 Schematic (3.8L "W" Body) EGR Fault. Scheme 193

Code 53, 54 & 55 Flow Chart (3.8L (VIN L) Except "E" Body) EGR Fault. Scheme 194

Check for poor harness connections or harness damage. If no problems are found, turn ignition on. Backprobe applicable PCM terminals with a DVOM while wiggling harness. If a failure is induced, voltage reading will change. If no problems are found, check for check EGR valve pintles and orifices for excessive carbon build-up. Also, check for plugged EGR tube or passages.

Code 54 & 55 Schematic (3.8L (VIN 1) "C" & "H" Bodies) EGR Fault. Scheme 195

Code 54 & 55 Flow Chart (3.8L (VIN 1) "C" & "H" Bodies) EGR Fault. Scheme 196

Monitor voltage at each terminal shown in schematic while moving related harness connectors, including PCM harness. If failure is induced, voltage will change. This may help to isolate an intermittent condition. Check for bent pins at PCM. If code reoccurs with no apparent connection problem, replace PCM.

Code 56 Schematic (3.8L (VIN L) "C" & "H" Bodies) Quad-Driver Error. Scheme 197

Code 56 Schematic (3.8L (VIN 1) "C" & "H" Bodies) Quad-Driver Error. Scheme 198

Code 56 Schematic (3.8L "W" Bodies) Quad-Driver Error. Scheme 199

Code 56 Flow Chart (3.8L Except "E" Body)(1 Of 2) Quad-Driver Error. Scheme 200

A cruise control throttle cable which binds or intermittently sticks can cause a Code 63 to set. Outside electrical interference (such as a CB antenna lead near the PCM wiring harness) may induce a false servo position signal and set Code 63.

Code 63 Flow Chart (3.8L Except "E" Body) Cruise System Problem. Scheme 201

Outside interference such as CB antenna lead near PCM wiring harness may cause false servo position sensor signal and set Code 68.

Code 68 Flow Chart Using Tech 1 (3.8L) Cruise System Problem. Scheme 202