Guide To P0170 OBD Error Code Solutions

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If you feel sudden drop in the engine performance and continuous stalling and hard idles along with flashing of check engine lights on the dashboard, this may be an indication of OBD Code P0170 being stored in the PCM/ECM.

When the OBD code P0170 error is set, it means that the powertrain control module is detecting a fuel trim that is outside the range of specification set by the vehicle’s manufacturer. This can mean a negative fuel trim or a positive fuel trim has been detected.

The powertrain control module receives a signal from the oxygen sensors and will adjust the amount of fuel the engine receives based on the readings provided by the oxygen sensors. This action carried out by the powertrain control module is called a fuel trim.

If the signal from the oxygen sensors calls for less fuel, the powertrain control module will act out a negative fuel trim. If the oxygen sensors call for a fuel increase, the powertrain control module will act out a positive fuel trim.

What causes the problem of Fuel Trim Malfunction (Bank 1)?

• Intake air leakages
• Faulty/damaged front heated oxygen sensor
• Engine misfiring
• Faulty fuel injection system
• Exhaust gas leakages
• Wrong fuel pressure
• Lack of engine oil
• Faulty Mass Air Flow (MAF) sensor
• Incorrect Positive Crankcase Ventilation (PCV) hose connection

1. Powertrain Control Module - PCM issues directly affects the engine control and transmission control module. Thus, replace faulty components now.
2. Oxygen Sensor Cable - Check for faulty sensor cables that will not be able to transmit the data properly and needs to be replaced immediately.
3. Catalytic Converter - Sometimes catalytic converters can overheat and become faulty. Replace your old catalytic converter now!
4. Exhaust System - Replace damaged exhaust parts immediately as a damaged one hampers the fuel economy and thus the performance.
5. Mass Air Flow Sensor - Faulty MAF sensor can cause engine to run rich or lean under load, decrease fuel efficiency and because rough engine idles. Thus, replace them now!
6. Diagnostic Tools - Find wide range of diagnostic tools to detect and correct the OBD code error
   

The vehicle's ECU runs checks on sensors multiple times a second. When the ECU finds fuel trim specification out of specified limits, it causes a Check Engine Light to illuminate. This results in wrong readings from the heated oxygen sensor. It can also lead to vehicle running poorly and a decrease in fuel efficiency along with frequent stalling and increased emissions.

Common Symptoms

• Decreased fuel economy
• Stalling engine
• Loss of acceleration and power
• Check engine light illumination.

• Correct any condition that causes the engine to run rich
• Correct any condition that causes the engine to run lean
• Replace the powertrain control module

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• Put the OBD-II scanner in vehicle's OBD-II port to confirm presence of P0170 error code.
• Freeze frame the data and vehicle speed, operating temperature, engine speed, and operating time is checked for when the code was detected.
• Perform a road test with a scan tool installed in the OBD-II port to confirm an issue is present.
• Visually inspect the wiring on both oxygen sensors for damaged/broken wiring, swapped connectors, or wiring shorted to ground or power. Use a multimeter to check that no wiring the distorted or short.
• Poor quality replacement catalytic converters are susceptible to repeated failure and should be avoided and replaced with a quality one.
• Search technical service bulletins (TSB) in your vehicle information source. If you find one that matches the symptoms and code/s presented by the vehicle in question, it will very likely aid you in your diagnosis. TSB listings are compiled from thousands of successful repairs.
• Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may
• have to be allowed to worsen before a correct diagnosis can be made. If the code persists, then
• you should begin your diagnosis by determining whether the fuel trim level is negative or positive.
• Once this is determined, proceed with testing the engine and fuel system for proper operation
• (including testing fuel pressure, inspecting for vacuum leaks, etc.). If these factors are found to
• be within the required specifications, then begin testing engine sensors, electrical wiring and
• connectors, as well as the PCM. Since mass air flow failure is by far the most common cause of
• this code, here is the process for diagnosing it.
• Using the scanner (with the data stream narrowed to include only the mass air flow) observe the
• sensor reading in grams per second and compare your findings with the manufacturer’s specified
• reference value at varying RPMs.
• If actual data fails to coincide with the manufacturer’s specifications, replace the mass air flow sensor with an OEM quality part and retest. If the mass air flow sensor checks out, monitor oxygen sensor voltage using the scanner.
• Check for fuel pump, if a lean exhaust condition is indicated to make sure that it is making sufficient pressure and inspect the fuel system for leaks.
• Check the fuel pressure regulator for internal fuel leaks and proper operation
• Replace and repair fuel delivery components as required and retest the system to ensure a successful repair has been performed. Also check for vacuum leaks at vacuum hoses, throttle body gaskets, and intake gaskets.
• Also check for any fault in the PCM and do the reprogramming as required.

Common mistakes when diagnosing the P0170 code

It is always important to have engine issues diagnosed by a certified mechanic who follows the correct diagnostic procedures.

• Intake Manifold vacuum leaks
• Check for Defective Mass Air Flow Sensor
• Inspect and replace Defective Mass Air Flow Sensor wiring or connections