Lexus NX: Rough Idling (P1605)
DESCRIPTION
When the engine is idling stably under a low load, if the idle speed drops or becomes unstable, this DTC will be stored.
Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was moving or stationary, whether the engine was warmed up or not, whether the air fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.
| DTC No. | Detection Item | DTC Detection Condition | Trouble Area | MIL | Memory |
|---|---|---|---|---|---|
| P1605 | Rough Idling | After 5 seconds or more elapse after starting the engine, with the engine running, the engine speed drops to 400 rpm or less (1 trip detection logic) | - | Does not come on | DTC Stored |
CAUTION / NOTICE / HINT
HINT:
-
In contrast to normal malfunction diagnosis for components, circuit and systems, DTC P1605 is used to determine the malfunctioning area from the problem symptoms and freeze frame data when the user mentions problems such as rough idling.
As these DTCs can be stored as a result of certain user actions, even if these DTCs are output, if the customer makes no mention of problems, clear these DTCs without performing any troubleshooting and return the vehicle to the customer.
- If any DTCs other than P1605 are output, troubleshoot those DTCs first.
- Since DTC P1605 is different from other DTCs, the following procedure is shown as a reference.
- Read freeze frame data using the Techstream. Freeze frame data records engine conditions when a malfunction occurs. This information can be useful when troubleshooting.
-
When confirming the freeze frame data, be sure to check all 5 sets of freeze frame data.
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- When confirming freeze frame data, if there are multiple items related to the cause of the malfunction, perform troubleshooting for all related items.
- Try to operate the vehicle under the conditions recorded in the freeze frame data which were present when the malfunction occurred. Confirm the data at this time and the data when the engine is idling (engine warmed up and no load) and compare these data with the freeze frame data.
- Inspections take into account the fact that the malfunction may not have reoccurred and place emphasis on checking the vehicle conditions present at the time the malfunction occurred.
- When performing inspections, jiggle the relevant wire harnesses and connectors in an attempt to reproduce malfunctions that do not always occur.
PROCEDURE
| 1. | CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P1605) |
(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (IG).
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(e) Read the DTCs.
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| Result | Proceed to |
|---|---|
| DTC P1605 is output | A |
| DTC P1605 and other DTCs are output | B |
HINT:
If any DTCs other than P1605 are output, troubleshoot those DTCs first.
| B | .gif) | GO TO DTC CHART |
|
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| 2. | CHECK FREEZE FRAME DATA |
(a) Turn the Techstream on.
(b) Check the following freeze frame data to see if the engine was cold or warm when the freeze frame data was recorded.
Confirmation Item| Coolant Temp |
| Initial Engine Coolant Temp |
(c) Check the following freeze frame data to see if the vehicle was idling.
Confirmation Item| Engine Speed |
(d) Check the following freeze frame data to see purge VSV operation when the freeze frame data was recorded.
Confirmation Item| EVAP (Purge) VSV |
| Evap Purge Flow |
| Purge Density Learn Value |
| EVAP Purge VSV |
(e) Check the following freeze frame data to see engine idle operating conditions recorded.
Confirmation Item| Throttle Position |
| ISC Flow |
| ISC Position |
| Idle Spark Advn Ctrl #1 |
| Idle Spark Advn Ctrl #2 |
| Idle Spark Advn Ctrl #3 |
| Idle Spark Advn Ctrl #4 |
| ISC Feedback Value |
| ISC Learning Value |
| Electric Load Feedback Value |
| Air Conditioner FB Val |
| Low Revolution Control |
| MAP |
| EGR Step Position |
(f) Check the following freeze frame data to see the engine load and electric load.
Confirmation Item| Calculate Load |
| Electric Fan Motor |
(g) Use this information to perform a simulation test.
(h) Compare the "Normal Condition" information in the Data List table (reference values) with the freeze frame data listed above and with the simulation test results to determine the problem cause.
| Result | Proceed to |
|---|---|
| The problem cause can be determined | A |
| The problem cause cannot be determined | B |
| A | | REPAIR OR REPLACE MALFUNCTIONING PARTS |
| B | | CHECK FOR INTERMITTENT PROBLEMS |
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