Fix P0650: Mechanic’s solutions that WORKED

The P0650: Malfunction Indicator Lamp (MIL) Control Circuit points out a fault in the Malfunction Indicator Lamp control circuit, which is responsible for illuminating the check engine light on the vehicle’s dashboard. This light is crucial as it alerts the driver to potential engine issues. A malfunction in this system could prevent the driver from being notified of existing problems.

P0650 quick overview

Meaning	P0650: Malfunction Indicator Lamp (MIL) Control Circuit
Is it serious?	This code can be serious as it indicates a malfunction in the vehicle’s self-diagnostic system, potentially masking other critical issues.
Possible causes	– Faulty or burned-out Malfunction Indicator Lamp (MIL) bulb – Issues with the wiring or connectors between the ECM and the MIL – Malfunctioning or damaged ECM (Engine Control Module) – Ground circuit issues – Short circuits or open circuits in the MIL control circuit
How to diagnose?	Check MIL Bulb: Verify the bulb’s functionality; replace if faulty. Inspect Wiring and Connectors: Examine the wiring and connectors between the ECM and the instrument cluster for damage or corrosion. Test ECM Grounds: Ensure the ECM is properly grounded. Ground MIL Circuit: Temporarily ground the MIL circuit at the ECM to test if the light activates. ECM Diagnostic: Conduct diagnostics on the ECM to check for internal faults. Check for Updates: Ensure the ECM’s software is up-to-date. Inspect Instrument Cluster: Verify that the instrument cluster, including the MIL, is functioning correctly.

How to fix P0650 – learn from mechanics

I looked into P0650 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Nissan

Vehicle Information: 2003 Nissan Altima SE 3.5L

Issue + Repair History:

• Customer reported inability to accelerate and the check engine light being on.
• Found codes P0650, P0507, and P0128.
• Thermostat replaced for P0128.
• Instrument cluster replaced for P0650.
• The issue reoccurred with codes P0650 and P0507 returning.
• The vehicle drives fine currently, but the issue is expected to return.

Other OBD2 Codes + Test Results:

• P0650: MIL Control Circuit Malfunction
• P0507: Idle Air Control System RPM Higher Than Expected

Suggestions to Fix Issue:

• Complete the idle relearn procedure for P0507.
• For P0650, conduct circuit tests as per the service manual.
• Consider the possibility of a faulty ECM.
• Inspect wiring for insulation damage or short circuits.

Final Fix:

• Replacing the ECM resolved the issue. After installation, the ECM was reprogrammed by the dealer, and the vehicle ran well without any pending codes.

Case #2: Hyundai

Vehicle Information: 2005 Hyundai Accent GLS 1.6L

Issue + Repair History:

• Customer complaint: Check engine light on, code P0650.
• PCM replaced for the same code.
• Resistance checked from PCM to cluster harness connector.
• Harness checked for shorts to ground.
• Discovered a TACU module from an ’03 Hyundai Accent in the vehicle, potentially incompatible with the ’05 model.

Other OBD2 Codes + Test Results:

• P0650: MIL Internal Fault

Suggestions to Fix Issue:

• Check the voltage drop through the ECM, especially on the ECM side of the MIL.
• Verify the connections at various connectors (M71, MC01, C26).
• Ensure ECM software is up to date.
• Check ECM grounds (G10 and G11) at the left kick panel.
• Conduct a thorough check of the wiring harness.
• Consider potential issues with the ignition switch, aftermarket installations, or instrument cluster.
• Consider replacing the bulb and conducting a voltage drop test on MIL lamp wires.

Final Fix:

• Replacing the bulb resolved the issue. Monitors were set without problems, and the vehicle passed California smog testing.

Case #3: Pontiac

Vehicle Information: 2003 Pontiac Bonneville SE 3.8L

Issue + Repair History:

• MIL light on, two EVAP codes and P0650 code found.
• Replaced leaky seal on fuel pump module and vent solenoid.
• P0650 code returned on first start.
• O2 sensor heater and EGR monitors not running.
• Replaced front O2 sensor, cleaned EGR, had computer flashed.
• Found additional code P01670 (driver module circuit 4).
• Replaced PCV valve, seals, and cap.

Other OBD2 Codes + Test Results:

• P0650: MIL Light Circuit
• P1670: Driver Module Circuit 4

Suggestions to Fix Issue:

• Check voltage at PCM Connector C2, pin 5 (brown and white wire) for battery voltage KOEO.
• Inspect PCM connector C2 for corrosion and apply stabilant.
• Recheck all ground wires.
• Remove both battery cables, touch them together for one hour, then reconnect.
• Check the operation of the EGR monitor via scan tool.
• Examine PCV seals and replace if needed.

Final Fix:

• Replacing the PCM fixed the P0650 code.
• EGR monitor ran after replacing PCV valve, seals, and cap.

Case #4: Volvo

Vehicle Information: 1999 Volvo V70 GLT 2.4L

Issue + Repair History:

• Initial issue: intermittent hesitation and stalling, ETS light on.
• Check engine light bulb removed/burnt out.
• Multiple codes, excluding P0650.
• Replaced throttle module assembly with a used one from eBay.
• After installation, engine starts, runs for a few seconds, then shuts off. ETS light on continuously.
• Question regarding software reprogramming for throttle body replacement.

Other OBD2 Codes + Test Results:

• P1113: Ambient air temperature, HVAC.
• P0650: MIL light output.

Suggestions to Fix Issue:

• Verify compatibility of used throttle module with the specific year model.
• Check if throttle module requires programming using Volvo VIDA software.
• Explore the possibility of programming with alternative tools, like Autologic.
• Inspect the relay that controls the throttle body.
• Verify if the throttle module has a white or yellow sticker (white original, yellow upgraded).

Final Fix:

• Replaced the throttle plate assembly with a used one matching the original’s numbers.
• No reprogramming was required as numbers were identical.
• Issue resolved, ETS light off, engine running normally.

Case #5: Nissan

Vehicle Information: 2002 Nissan Altima SE 3.5L

Issue + Repair History:

• Customer complaint: vehicle cutting out over 2500 RPM, no MIL light, code P0650.
• Other codes found: P0011 (IVT Control Bank 1) and P0012 (IVT Control Bank 2).
• Suspected the ECM was causing the fuel cutoff at 2500rpm due to the MIL circuit not working.
• Attempted to diagnose and fix MIL light issue.

Other OBD2 Codes + Test Results:

• P0650: Malfunction Indicator (MIL) Control Circuit

Suggestions to Fix Issue:

• Suggested to ground the wire from the cluster to the ECM to test if it would turn the MIL light on.
• Recommended checking ECM’s ability to provide ground circuit for the MIL.
• Advised to examine the charging system and potential water damage at connectors.
• Consideration of the possibility of a faulty ECM.

Final Fix:

• Grounding the wire at the ECM did turn the MIL light on.
• Replaced the ECM, which resolved the MIL light issue.
• Required programming of ignition keys into the ECM due to the immobilizer part of the security system.
• Intake variable valve control did not present further problems.

Advice	Description of Diagnostic Step
Check ECM Grounds	Verify that the ECM has proper grounding; a faulty ground can lead to issues with the MIL circuit.
Inspect Wiring and Connectors	Examine the wiring and connectors for damage, corrosion, or loose connections, particularly between the ECM and the instrument cluster.
Test MIL Light Operation	Ground the wire from the cluster to the ECM to see if it turns the MIL light on, indicating whether the issue is with the ECM’s control circuit.
Replace ECM if Necessary	If diagnostics point towards a malfunctioning ECM, consider replacing it as it could be the root cause of the P0650 code.
Update ECM Software	Ensure that the ECM software is up-to-date, as outdated software might contribute to the malfunction indicator light issues.
Check for External Interference	Look for potential external factors like installed aftermarket equipment that could interfere with the MIL circuit.
Test Instrument Cluster	Ensure that the instrument cluster, including the MIL light, is functioning properly. Replace if necessary.