Engine Controls - Tests W/codes - Except Obd-Ii: Diagnosis

Test Mode

This mode detects same malfunctions as normal mode. It also detects malfunctions in starter signal circuit, idle contact signal of throttle position sensor, A/C signal, neutral start switch signal (M/T) and park/neutral start switch (A/T). Test mode is more sensitive to intermittent and regular faults, and is used for road test conditions.
Before retrieving trouble code(s), verify MIL on instrument panel comes on with ignition on and engine off. The MIL light should go off when engine is started.
If MIL does not come on with ignition on and engine off, check bulb circuit on instrument panel and wiring circuit between MIL and ECM. See appropriate wiring diagram in «WIRING DIAGRAMS»(ref-21772) article. If MIL remains on, self-diagnostic system has detected a malfunction or abnormality.
To read diagnostic codes, ensure battery voltage is at least 11 volts, throttle valve is fully closed, transmission is in Neutral, all accessories are off and parking brake is applied. Turn ignition off. Locate Data Link Connector No. 2 (DLC2). see scheme 1 Using a jumper wire, connect terminals E1 and TE2 of DLC2. see scheme 2 Turn ignition on. DO NOT start engine. NOTE: If terminals E1 and TE2 are connected after ignition is turned on, test mode will not start.
When ignition is turned on, Malfunction Indicator Light (MIL) on instrument panel should flash. If MIL does not flash, see «MALFUNCTION INDICATOR LIGHT (MIL) DOES NOT FLASH»(ref-21749-S03747874692001010300000).
Start engine. Perform road test and simulate conditions described by customer. DO NOT disconnect jumper wire connecting terminals E1 and TE2. After road test, connect another jumper wire between terminals E1 and TE1 of DLC No. 1 or 2.
Count number of flashes from MIL. System is functioning properly (normal condition) if MIL flashes 2 times every second. If a diagnostic trouble code is displayed, first group of flashes will indicate first digit of a 2-digit diagnostic code. After a 1.5 second delay, second group of flashes will indicate second digit of diagnostic code.
If more than one code is stored, a 2.5 second delay will occur between diagnostic codes. After all diagnostic codes have been displayed, a 4.5 second delay will occur and then codes will be repeated until jumper wire connecting terminals E1 and TE1 is disconnected. Diagnostic codes will display from smallest to largest number.
After completing check, disconnect jumper wires that connect terminals TE1 and TE2 to terminal E1 on DLC. Diagnostic Code 43 will set if engine is not cranked when entering test mode. This is normal. If automatic transmission is in "D", 2, "L" or "R", A/C switch is in ON position or accelerator pedal is depressed, Code 51 will set. This is normal.
Identify and record diagnostic trouble codes. See «NOTES ON TROUBLE CODES»(ref-21749-S27653218752001010300000). For additional information on trouble codes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-21749-S05363343442001010300000) table and appropriate DIAGNOSTIC TROUBLE CODE IDENTIFICATION table. After reading diagnostic trouble code definition and identification, perform appropriate diagnostic trouble code chart. To clear codes, see «CLEARING CODES»(ref-21749-S33568400162001010300000).

Momentary Interruption Test

If Code 13, 22, 24, 41 or 47 is stored in ECM memory during diagnosis and no trouble can be found with these circuits, perform MOMENTARY INTERRUPTION TEST.

Clear codes from ECM memory. See «CLEARING CODES»(ref-21749-S33568400162001010300000). With ignition off, connect a jumper wire between terminals E1 and TE2 of DLC No. 1 or 2. see scheme 2
Start engine. Ensure MIL goes out. Pull lightly on wires, and apply vibration to connectors and relays associated with diagnostic code that is set.
If MIL illuminates during this test, a fault is in indicated connector or location in wiring harness. Repair as necessary.
Clear diagnostic codes. Start engine. If MIL does not go out, check thoroughly for faulty connections. Perform MOMENTARY INTERRUPTION TEST again. If MIL still will not go out, check and replace ECM as necessary. See COMPUTERIZED ENGINE CONTROLS in appropriate «SYSTEM/COMPONENT TESTS»(ref-21748) article.

Note. Electronically Controlled Transaxle/Transmission (ECT) uses same ECM as EFI system. For ECT diagnostics, see the TRANSMISSION SERVICING article.

NOTES ON TROUBLE CODES

When certain malfunctions or trouble codes initially occur, they will be temporarily stored in ECM memory, but MIL on instrument panel will not come on.
The second time malfunction or trouble code is detected, MIL on instrument panel will then come on, provided ignition is turned off and then back on after malfunction or trouble code was first detected. This is referred to as the Two Trip Detection Logic and only applies to specified trouble codes. See «TWO TRIP DETECTION LOGIC TROUBLE CODES»(ref-21749-S42006012252001010300000) table.
In Normal Mode, MIL on instrument panel will go off after malfunction is repaired, but all trouble codes except ECM non-memory Trouble Codes 16, 43, 51 and 53 will be retained in ECM memory until cleared. ECM non-memory trouble codes are not stored in ECM memory.
In Test Mode, all trouble codes except ECM non-memory Trouble Codes 16, 43, 51 and 53 are retained in ECM memory, even with ignition off and repairs made, until cleared.

Note. When road testing vehicle in Test Mode, the Two Trip Detection Logic will not function. In Test Mode, the MIL on instrument panel will come on the first time malfunction or trouble code is detected.

Application	Trouble Code
GS300	21, 25, 26, 28 & 78

TWO TRIP DETECTION LOGIC TROUBLE CODES

Note. When in Test Mode, if vehicle is not driven at a speed greater than 6 MPH, ECM will set Trouble Codes 42 and 43. For MIL operation in relation to trouble code when in Test Mode, see appropriate TROUBLE CODE IDENTIFICATION table under TROUBLE CODE IDENTIFICATION .

TEST PREPARATION

Manufacturer recommends using Check Harness "A" (09990-01000) when using diagnostic code charts to diagnose malfunctions. Check harness "A" is a test harness that is installed between Electronic Control Module (ECM) and ECM connector. Voltage and resistance readings are taken at check harness connectors. NOTE: Always check and note diagnostic trouble codes prior to disconnecting ECM connector. Disconnecting ECM connector will erase codes from memory.
To install check harness "A", ensure ignition switch is in the OFF position. Disconnect ECM connector. ECM is located underneath top of passenger-side carpet and is mounted to floor panel. Connect check harness "A" between ECM and ECM connector. Terminal arrangement of check connector is the same as those on the ECM. Proceed to appropriate diagnostic trouble code chart.

TROUBLE CODE DETECTION DRIVING PATTERN TEST

Note. Trouble code driving pattern test may be referred to as driving pattern test.

On certain trouble codes, once trouble code has been cleared from ECM memory, a trouble code detection driving pattern test can be performed to verify repairs made and that trouble code does not reset. The trouble code driving pattern test will duplicate the conditions required to set specified trouble codes.
Trouble code detection driving pattern test lists the procedure to be performed to check that trouble code does not reset. Trouble code detection driving pattern tests apply only to specified trouble codes. Trouble code detection driving pattern test will be included with proper trouble code chart under DIAGNOSTIC CODE CHARTS.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

Code	Definition
12	No "G", "G1", "G2" or "NE" Ignition Signal To ECM Within 2 Seconds After Engine Is Cranked, Open In "G-" Circuit
13	No "NE" Ignition Signal To ECM When Engine Speed Is Greater Than Approximately 1000 RPM, "NE" Signal Does Not Pulse 12 Times To ECM During Interval Between "G1" and "G2" Pulses
14	No "IGF" Ignition Signal To ECM From Ignitor Several Times In Succession
15	No "IGF" Ignition Signal To ECM From Ignitor Several Times In Succession
16	Fault In Communications Between Engine Central Processing Unit (CPU) and Electronic Controlled Transmission (ECT) CPU In ECM
21	Defective O2 Sensor, Open Or Short Circuit In O2 Sensor Signal
22	Open Or Short Circuit In Engine Coolant Temp. Sensor Signal
24	Open Or Short Circuit In Intake Air Temp. Sensor Signal
25	Lean Signal Sent By O2 Sensor For Several Seconds
26	Rich Signal Sent By O2 Sensor For Several Seconds
27	Open Or Short Circuit In Sub-O2 Sensor Signal
28	Defective O2 Sensor, Open Or Short Circuit In O2 Sensor Signal
29	Open Or Short Circuit In Sub-O2 Sensor Signal
31	Open Or Short Circuit In Airflow Meter Or MAP Sensor Signal
35	Open Or Short Circuit In BARO Sensor
41	Open Or Short Circuit In Throttle Position Sensor Signal
42	No Signal From Vehicle Speed Sensor For Several Seconds
43	No Starter Signal To ECM
47	Open Or Short Circuit In Sub-Throttle Position Sensor Signal
48	Open Or Short Circuit In Vacuum Switching Circuit Of Air Switching Valve
51	(2) Problem In One Of 3 Circuits Monitored By ECM
52	Open Or Short Circuit In Knock Sensor Signal
53	Knock Control In ECM Is Faulty
55	Open Or Short Circuit In Knock Sensor Signal
71	EGR Gas Temp. Less Than Predetermined Level During EGR Control
78	Open Or Short Circuit In Fuel Pump Control Circuit Or Fuel Pump Electronic Control Unit (ECU)
(1) Listed are possible areas causing trouble codes. Not all trouble codes are used on all models. (2) Throttle position sensor, Park/Neutral switch and A/C Signal circuits are monitored.