Engine Controls - Self-Diagnostics - 350Z: Diagnosis Nissan 350Z I

ON-BOARD DIAGNOSTICS

ECM detects malfunctions related to engine sensors or actuators. OBD-II monitors emission related components and can store Diagnostic Trouble Codes (DTCs), 1st trip DTCs, freeze-frame data, 1st trip freeze-frame data and System Readiness Test (SRT) information. Using a scan tool, this data and DTC information can be retrieved to assist in diagnosing problems. The Malfunction Indicator Light (MIL) can be used for code retrieval and fuel feedback monitoring.

When a malfunction is detected for the first time, the 1st trip DTC and 1st trip freeze frame data are stored in Engine Control Module (ECM) memory. However, in most instances, MIL will not be illuminated. If the same malfunction is detected on the next trip (under similar conditions), MIL will be illuminated and a DTC is stored (2nd trip detection logic). If a misfire or fuel system malfunction should occur during 1st trip, MIL may be illuminated or flash. DTC and freeze-frame information will be stored to aid in diagnostics by specifying operating conditions when DTC was set.

TESTING PROCEDURE

To ensure correct diagnosis and repair, testing should be done in the following order

1. Get information about conditions present when malfunction occurred. Retrieve and record DTCs and freeze-frame data. See «RETRIEVING DIAGNOSTIC TROUBLE CODES»(ref-159515-S23523799002003121500000) . If MIL is on, and DTCs are not accessible, check for ECM fail-safe mode. See «FAIL-SAFE MODES»(ref-159515-S30917862372003121500000) . If symptoms exist, but DTCs or freeze-frame data do not exist, go to next step. If symptoms do not exist, but DTCs or freeze-frame data exist, go to step 5 .
2. Attempt to duplicate conditions present when malfunction occurred. If malfunction is detected, perform basic inspection. See «ON-VEHICLE ADJUSTMENTS»(ref-151928) article. If using CONSULT-II, go to next step. If using generic scan tool, go to step 4 .
3. Check inputs and outputs in DATA MONITOR (SPEC) mode with CONSULT-II. See «DATA MONITOR (SPEC) MODE»(ref-159515-S37470729902003121500000) under CONSULT-II under SCAN TOOL USAGE. Compare readings with specifications listed in «PIN VOLTAGE CHARTS»(ref-151939) article. If problem is found, repair as necessary. If problem is not found, go to next step.
4. Go to «TROUBLE SHOOTING - NO CODES»(ref-151937) article for diagnosis by symptom. If malfunction cannot be verified, problem may be intermittent. See «INTERMITTENTS»(ref-151937-S26600594012003010900000) in «TROUBLE SHOOTING - NO CODES»(ref-151937) article.
5. Clear DTCs and freeze-frame data. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-159515-S02623607512003121500000) . Attempt to reset DTC by performing DTC CONFIRMATION PROCEDURE in appropriate diagnostic test. If multiple DTCs are present, diagnose in order of priority. See «MULTIPLE DTC PRIORITY IDENTIFICATION»(ref-159515-S34722225602003121500000) table. If DTC does not reset, problem may be intermittent. See «INTERMITTENTS»(ref-151937-S26600594012003010900000) in «TROUBLE SHOOTING - NO CODES»(ref-151937) article. If DTC resets, go to next step.
6. Perform appropriate diagnostic procedure under «DIAGNOSTIC TESTS»(ref-159515-S09051351382003121500000) . After repairs are made, perform appropriate DTC CONFIRMATION PROCEDURE to verify repair. Clear DTCs. If SRT codes are not set, drive vehicle in specified driving pattern to set all SRT codes. See «SYSTEM READINESS TEST»(ref-159515-S20297660732003121500000) .

MULTIPLE DTC PRIORITY IDENTIFICATION

Using Scan Tool

See SCAN TOOL USAGE .

Diagnostic Test Mode II (Self-Diagnostic Results)

In this mode, DTCs and 1st trip DTCs are indicated by the number of MIL flashes. DTCs and 1st trip DTCs are displayed at the same time. If MIL does not illuminate when engine is running in diagnostic test mode I, all displayed items are 1st trip DTCs. If MIL is illuminated when engine is running in diagnostic test mode I, and only one DTC is indicated, it is a DTC. If 2 or more DTCs are indicated, they may be either DTCs or 1st trip DTCs.

A particular DTC can be identified by the number of 4-digit numeral flashes. The zero is indicated by 10 flashes. The length of time the 1000th-digit numeral flashes on and off is 1.2 seconds consisting of an ON (0.6-second)-OFF (0.6-second) cycle. The 100th-digit numeral and lower digit numerals consist of a 0.3-second ON and 0.3-second OFF cycle. A change from one digit numeral to another occurs at an interval of 1.0-second OFF. In other words, the later numeral appears on the display 1.3 seconds after the former numeral has disappeared. A change from one trouble code to another occurs at an interval of 1.8-second OFF. In this way, all the detected malfunctions are classified by their DTC numbers. (Scheme 355)

Scheme 355

Diagnostic Test Mode II (Front HO2S Monitor)

In this mode, MIL displays fuel mixture condition (lean or rich), as monitored by front HO2S. MIL is on when mixture is lean and off when mixture is rich. Therefore, a flashing MIL indicates closed loop fuel control and a MIL that remains on or off indicates open loop.

To check front HO2S function, start engine in diagnostic test mode II. See ENTERING DIAGNOSTIC TEST MODE II (FRONT HO2S MONITORING) . Warm engine to normal operating temperature. Run engine at 2000 RPM for 2 minutes. MIL should come on more than 5 times within 10 seconds with engine running at 2000 RPM.

Entering Diagnostic Test Mode II (Self-Diagnostic Results Mode)

Note. Switching diagnostic test modes is impossible if accelerator pedal position sensor circuit has a malfunction. ECM always returns to diagnostic test mode I after ignition is turned off.

1. Ensure accelerator pedal is fully released. Turn ignition on and wait 3 seconds.
2. Repeat the following 5 times within 5 seconds. Fully depress accelerator pedal. Fully release accelerator pedal.
3. Wait 7 seconds. Fully depress accelerator pedal, and hold for about 10 seconds until MIL starts flashing.
4. Fully release accelerator pedal. ECM is now in diagnostic test mode II.

Entering Diagnostic Test Mode II (Front HO2S Monitoring)

1. Enter self-diagnostic results mode. See «ENTERING DIAGNOSTIC TEST MODE II (SELF-DIAGNOSTIC RESULTS MODE)»(ref-159515-S09873173942003121500000).
2. Start engine. ECM has now entered front HO2S monitoring.
3. To switch from bank 1 to bank 2 or from bank 2 to bank 1, fully depress and release accelerator pedal quickly.
4. Ensure monitoring sensor has changed by flashing MIL as shown in illustration. (Scheme 356)

Scheme 356

CLEARING DIAGNOSTIC TROUBLE CODES

Note. If battery is disconnected for a prolonged period of time, all diagnostic information is cleared.

Using Generic Scan Tool

If ignition is on, turn ignition off and wait at least 10 seconds. Turn ignition on. Select MODE 4 or follow scan tool manufacturer's instructions.

Entering Diagnostic Test Modes

Turn ignition off. Connect scan tool to DLC. (Scheme 357) Turn ignition on. Press START on scan tool. Press ENGINE. Select one of the following diagnostic test modes

1. WORK SUPPORT This mode enables a technician to adjust some devices faster and more accurately by following indications on CONSULT-II unit. See «WORK SUPPORT MODE»(ref-159515-S15497638412003121500000) .
2. SELF-DIAGNOSTIC RESULTS Self-diagnostic results such as 1st trip DTC, DTCs, 1st trip freeze frame data or freeze frame data can be read and erased quickly. See «SELF-DIAGNOSTIC RESULTS MODE»(ref-159515-S02545130262003121500000) .
3. DATA MONITOR Input/output data in ECM can be read. See «DATA MONITOR MODE»(ref-159515-S40943967372003121500000) .
4. DATA MONITOR (SPEC) Input/output specification of basic fuel schedule, AFM, A/F feedback control value and other data monitor items can be read. See «DATA MONITOR (SPEC) MODE»(ref-159515-S37470729902003121500000) .
5. ACTIVE TEST Diagnostic test mode in which CONSULT-II drives some actuators apart from ECMs and also shifts some parameters in a specified range. See «ACTIVE TEST MODE»(ref-159515-S20741030642003121500000) .
6. DTC & SRT CONFIRMATION The status of system monitoring tests and self-diagnosis status/result can be confirmed.
7. ECM PART NUMBER ECM part number can be read.

Scheme 357

Active Test Mode

For ACTIVE TEST mode descriptions (Scheme 358)

Scheme 358

GENERIC SCAN TOOL

An OBD-II scan tool complying with SAE J1978 has the following functions. For further information, see the appropriate operation manual supplied by scan tool manufacturer.

Mode 1: Readiness Test

This mode accesses current emission related data input and output values. In this mode, system status information is also monitored.

Mode 3: Diagnostic Trouble Codes (DTCs)

This mode gains access to emission-related powertrain DTCs stored by ECM. For DTC definitions, see DIAGNOSTIC TROUBLE CODE DEFINITIONS .

Mode 8: EVAP System Testing

This mode can close EVAP system with ignition on (engine off). The following components can be opened or closed

1. EVAP canister vent control can be opened.
2. Vacuum cut valve by-pass valve can be closed.

During the following conditions, mode 8 cannot function

1. Low ambient temperature or low fuel temperature.
2. Low battery voltage.
3. Engine running or ignition switch in the OFF position.
4. Too much pressure applied to EVAP system.

Checking SRT Code Status (Using Generic Scan Tool)

Select MODE 1 with scan tool, and observe SRT STATUS. An INCMP display for any SRT system indicates the self-diagnosis for that circuit is incomplete. SRT systems that have completed self-diagnosis will be indicated by CMPLT, indicating SRT is set. If any category is incomplete, go to SETTING SRT CODES.

Setting SRT Codes (Using Generic Scan Tool)

To set all SRT codes as complete, drive vehicle according to procedure shown in illustration. (Scheme 359) Perform driving procedure one or more times. If driving procedure is interrupted, repeat procedure. On A/T models, operate vehicle with shift lever in "D" position and overdrive turned on. On M/T models, operate vehicle normally, shifting at normal speeds.

Scheme 359

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DIAGNOSTIC TROUBLE CODE DEFINITIONS