Engine Controls - Self-Diagnostics - Introduction - Q45: Other Infiniti Q45 II

OBD-II

PCM detects malfunctions related to engine sensors or actuators. OBD-II continuously monitors emission related components and can set Diagnostic Trouble Codes (DTCs), 1st trip DTCs, freeze-frame data, 1st trip freeze-frame data and System Readiness Test (SRT) information. This data and DTC information can be retrieved to assist in diagnosing problems. Using the Malfunction Indicator Light (MIL) to access MIL codes is limited to code retrieval and fuel feedback monitoring, and is not recommended. It is recommended to use Generic Scan Tool (GST), or Nissan's CONSULT scan tool when performing self-diagnostic procedures, clearing PCM or performing a System Readiness Test (SRT).

When a malfunction is detected for the first time, the 1st trip DTC and 1st trip freeze frame data are stored in Powertrain Control Module (PCM) memory. However, in most instances 1st trip MIL will not be illuminated. If the same malfunction is detected on the next vehicle trip, MIL will be illuminated as soon as the DTC is detected (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.

FREEZE-FRAME DATA

Note. 1st trip freeze-frame data values can only be displayed with Nissan's CONSULT, and are not displayed on GST scan tool.

PCM records engine operating condition when an emission related fault is detected. This single "snapshot" is stored in PCM memory to aid in diagnostics by indicating conditions present when DTC is detected. Freeze-frame data is kept in order of priority. If low priority freeze-frame data (priority 1) is stored and another freeze-frame fault should occur, with the same priority, only the original freeze-frame data will remain. Always record this information when reviewing information.

If MIL should illuminate, indicating a 2nd trip malfunction or a higher priority code, the lower priority freeze-frame data would be replaced with the priority 2 or 3 freeze-frame data. Should a priority 3 malfunction occur (misfire, A/T or air/fuel system fault), then any other lower priority freeze-frame data would be replaced with priority 3 freeze-frame data. See FREEZE FRAME PRIORITY IDENTIFICATION table. This recorded data is useful for determining conditions in which the malfunction occurs.

Note. Only one 1st trip DTC and one freeze-frame data "snapshot" can be stored in PCM. If using GST, 1st trip DTC freeze-frame information may not be accessible. Use CONSULT to retrieve 1st trip DTC freeze-frame information.

FREEZE FRAME PRIORITY IDENTIFICATION

RETRIEVING CODES USING MIL

Note. CHECK ENGINE or SERVICE ENGINE SOON light is now referred to as Malfunction Indicator Light (MIL).

Turn ignition on. Verify MIL is properly illuminated. If MIL does not illuminate, repair MIL circuit. Turn mode selector switch on PCM fully clockwise. MIL should turn off. Wait 2 seconds, and turn mode selector fully counterclockwise. System is now in diagnostic test mode II. Retrieve Diagnostic Trouble Codes (DTCs) by observing MIL, and counting the number of flashes. Record all codes set and then go to appropriate test procedure. MIL DTC numbering is different than CONSULT or GST DTC numbering. See appropriate DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION table.

MIL Code Display

MIL Code is a 4 digit number indicated by 2 separate 2 digit numbers flashed by MIL. The 2 separate numbers are separated by a pause (.9 second). The first number will be long flashes (.6 second), and the second will be short flashes (.3 second). If there is more than one MIL DTC stored, there will be a 2.1 second pause between codes.

For example, 3 long (.6 second) flashes, a pause (.9 second), then followed by 3 short (.3 second) flashes of MIL indicate a MIL Code 0303. If 2 different MIL Codes are stored, such as 0406 and 0608, this would be displayed by 4 long flashes, pause, 6 short flashes, long pause, 6 long flashes, pause, 8 short flashes of MIL.

Erasing Stored Information

The following emission related information will be erased from PCM memory: DTCs stored, 1st trip DTCs, freeze frame data, 1st trip freeze frame data, System Readiness Test (SRT) codes and test values. To erase this information, turn ignition off. Turn mode selector lever on the PCM clockwise, wait 2 seconds and turn mode selector counterclockwise.

RETRIEVING CODES USING GST

Turn ignition off. Connect scan tool to DLC located under left side dash panel. (Scheme 74) Turn ignition on. Enter program desired on GST screen. Perform each diagnostic mode according to appropriate service procedure displayed on GST. For further information, see the appropriate operation manual supplied by generic scan tool manufacturer.

Scheme 74

Mode 2: Freeze Frame Data

This mode gains access to emission-related data value information stored by PCM during the freeze frame portion of self-diagnostic mode during engine operation and may or may not store a Diagnostic Trouble Code (DTC). In this mode, MIL should be off, unless a DTC is present.

Mode 4: Clearing Codes

This mode can clear all emission related diagnostic information for DTCs. These include

1. Clear number of DTCs (Mode 1).
2. Clear DTCs (Mode 3).
3. Clear freeze-frame data (Mode 2).
4. Reset status of system monitoring test (Mode 1).
5. Clear on board monitoring results (Mode 6 and 7).

Mode 6: On-Board Tests

This mode accesses the results of on board diagnostic monitoring tests of specific components and systems that are not continuously monitored.

Mode 7: On-Board Tests

This mode enables the off board test drive to obtain test results for emission-related powertrain components and systems that are continuously monitored during normal driving conditions.

FAIL-SAFE MODE

If any malfunctions are detected in Mass Airflow (MAF), Engine Coolant Temperature (ECT), Throttle Position (TP), Traction Control System (TCS) or Powertrain Control Module (PCM) due to an open or short circuit, PCM will enter a fail-safe mode. Driveability will be poor and the MIL will be illuminated. Preprogrammed values will be used for engine operating conditions when PCM goes into fail-safe mode. See FAIL-SAFE OPERATING CONDITIONS table. Refer to all diagnostic tests that apply for description and testing of circuit affected.

When a failure is detected in the Central Processing Unit (CPU) of PCM, MIL will be illuminated. When PCM is in fail-safe, fuel injection, ignition timing, fuel pump operation, IACV-AAC valve and cooling fan operation will be limited. DTC and other PCM information may not be accessible.

FAIL-SAFE OPERATING CONDITIONS

CLEARING CODES

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

Using MIL

Turn ignition off. Wait 5 seconds. Turn ignition on. Perform MIL diagnostics for stored DTCs. See RETRIEVING CODES USING MIL. Change diagnostic test mode selector switch on PCM from mode II to mode I.

Using GST

Turn ignition off. Connect GST to DLC. (Scheme 74) Turn ignition on. Enter CLEAR CODES or Mode 4 selection on GST menu.

FUEL FEEDBACK MONITORING USING MIL

1. Enter Mode II diagnostics using MIL. See «RETRIEVING CODES USING MIL»(ref-18059-S15111515062000122900000) under SELF-DIAGNOSTIC SYSTEMS. If engine is started at this stage, MIL will display condition of air/fuel mixture, monitored by the front Heated Oxygen Sensors (HO2S), whether the vehicle is in closed loop or open loop. With engine at normal operating temperature, run engine at about 2000 RPM for 2 minutes under no-load condition. MIL should flash 5 times every 10 seconds indicating normal operating condition of air/fuel mixture monitored by front HO2S(s).
2. When MIL is on, it indicates a lean condition. When MIL is off, it indicates a rich condition. MIL switching on and off indicates closed loop operation. If MIL remains on or off, it indicates an open loop condition.
3. To switch to opposing HO2S, turn diagnostic test mode selector on PCM fully clockwise, wait 2 seconds and turn mode selector fully counterclockwise. MIL will now indicate changing to opposing HO2S by rapidly flashing and returning to lean/rich cycling. HO2S feedback of the opposing bank HO2S will now be displayed by MIL.
4. Repeat step 2) to switch back to original HO2S feedback signal. Switch from bank to bank as necessary. To erase stored DTC information, go to ERASING STORED INFORMATION. See «RETRIEVING CODES USING MIL»(ref-18059-S15111515062000122900000) under SELF-DIAGNOSTIC SYSTEMS. To remain in Mode II, turn engine off and immediately turn ignition on. Turn mode selector on PCM fully clockwise within 5 seconds.

Checking SRT Code Status

With scan tool connected, choose SRT STATUS mode (with Nissan CONSULT scan tool), or MODE 1 (OBD-II) if using a generic scan tool. On Nissan CONSULT, select DTC CONFIRMATION and check SRT STATUS. On OBD-II scan tools, follow manufacturers instructions for accessing SRT STATUS. An INCMP display for any SRT system indicates the self-diagnosis for that circuit is incomplete. SRT systems that have passed self-diagnosis will be indicated by CMPLT, indicating SRT is set. If any category is incomplete, follow SETTING SRT CODES procedure to set all SRT codes.

Setting SRT Codes

To set all SRT codes as complete, self diagnosis for the items specified in appropriate SYSTEM READINESS TEST (SRT) CODE IDENTIFICATION table must be performed one or more times. With scan tool connected to Data Link Connector (DLC), start engine and allow vehicle to warm to operating temperature and coolant temperature greater than 158°F (70°C). Drive vehicle according to procedure shown in illustration. (Scheme 75) Perform driving procedure one or more times. If driving procedure is interrupted, repeat procedure. Operate vehicle with shift lever in "D" position and overdrive ON.

Scheme 75

SYSTEM READINESS TEST (SRT) CODE IDENTIFICATION (Q45)

FINAL CHECK FOR ALL CODE CHARTS

Unless otherwise instructed, perform following FINAL CHECK after each repair is completed.

1. Clear all DTCs stored in PCM memory. See «CLEARING CODES»(ref-18059-S40501561062000122900000) under SELF-DIAGNOSTIC SYSTEM.
2. Ensure pass code is displayed on scan tool, or by MIL in mode II.
3. Perform a test drive.
4. Verify no DTCs are present in PCM memory. If results are okay, inspection is complete. If results are not okay, repeat circuit test for remaining DTC(s).

Ensure PCM pin terminals and harness connector are not damaged.

SUMMARY

If no DTCs (or only pass codes) are present and driveability symptoms exist, or intermittent codes exist, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.