This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.
P1505 is an OBD-II Code that refers to Idle Speed Control Actuator Signal Low
A P1505 code is a diagnostic trouble code that occurs when the ECM/PCM detects a problem with the idle speed control (ISC) actuator circuit. The ISC actuator is responsible for controlling the engine’s idle speed by opening and closing the throttle valve. If the ISC actuator signal is low, it can cause the engine to idle too high or too low.
Common causes for this code include:
- The idle speed control valve harness may have damage to the wiring or its connectors open/shorted
- Faulty ISC actuator
- Faulty throttle position sensor (TPS)
- Dirty or restricted air filter
- Dirty or restricted throttle body
- Faulty ECM/PCM
The symptoms of a P1505 code are:
- Illuminated Check Engine Light
- Rough or erratic idle
- Engine may stall at idle
- Reduced fuel economy
To diagnose a P1505 DTC code, a technician would:
- Scan for codes in the ECM and look at the freeze frame data for failure.
- Visually inspect the wiring harness and connectors for damage or loose/corroded connections.
- Check the ISC actuator for proper operation.
- Check the TPS sensor for proper operation.
- Clean the throttle body and air filter as needed.
- Check the ECM/PCM for any stored codes or history codes that may help in diagnosis.
The following are some of the most common mistakes that a technician may make when diagnosing a P1505 code:
- Not thoroughly inspecting all the wiring and connectors for damage.
- Replacing the ISC actuator without first checking the ECM/PCM for any stored codes or history codes.
- Not cleaning the throttle body and air filter as needed.
How serious is this?
A P1505 code is a relatively minor code, but it can cause the engine to run poorly if not diagnosed and repaired in a timely manner.
What repairs can fix the code?
The following are solutions that may fix this problem:
- Broken or faulty wirings must be repaired or replaced
- Faulty ISC actuator must be replaced
- Faulty throttle position sensor must be replaced
- Dirty or restricted air filter must be cleaned or replaced
- Dirty or restricted throttle body must be cleaned
- Faulty ECM/PCM may need to be reprogrammed or replaced
A P1505 is related to and may be accompanied by the following codes:
P1506 – Idle Speed Control Circuit Open
P1507 – ISC System RPM Higher Than Expected
P1508 – ISC System RPM Lower Than Expected
In conclusion, the P1505 code is a diagnostic trouble code that refers to a problem with the idle speed control actuator circuit. The ISC actuator is responsible for controlling the engine’s idle speed by opening and closing the throttle valve. If the ISC actuator signal is low, it can cause the engine to idle too high or too low.
Possible causes for this code include: damaged wiring or connectors, a faulty ISC actuator, a faulty throttle position sensor, a dirty or restricted air filter, a dirty or restricted throttle body, or a faulty ECM/PCM.