The P0688 code is a generic powertrain code related to output circuit issues, including internal computer failures. In this case, the engine control module (ECM), also known as a powertrain control module (PCM) has signaled too much power to the power relay sense circuit, which powers the: ECM/PCM.

What does P0688 mean?

OBD-II Code P0688 is defined as a ECM/PCM Power Relay Sense Circuit/Open. The engine computer (PCM) power relay controls battery voltage to the PCM. If the PCM detects an incorrect voltage signal from the power relay, it will set code P0688. Driving with this trouble code is not recommended.

What does power relay Open mean?

A power relay is a device that uses an electromagnet to open or close a circuit when the input (coil) is correctly excited.

What does P0685 mean?

The voltage in the relay coil control circuit is normally low. If you see trouble code P0685, it means that the PCM’s fault detection circuit has detected voltage from the relay that measures above the normal parameters – above 4.6 volts with the key turned on.

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How do I fix code P0688?

What repairs can fix the P0688 code?

  1. Repair any loose or damaged battery cables.
  2. Fully charge the battery.
  3. Replace battery if needed.
  4. Replace damaged or blown fuses.
  5. Repair or replace damaged or corroded electrical wires and related connectors.
  6. Repair loose or shorted connections.
  7. Replace damaged or defective ECM/PCM relay.

Can you bypass ASD relay?

While it’s not smart to bypass an ASD relay because it serves an important safety role (it prevents the engine to overrev), sometimes it can stop you from starting your car. The easiest way to bypass an ASD Relay is with a wire.

What is ECM PCM power relay?

The engine control module (ECM) or powertrain control module (PCM) runs various processes in the engine and (in the case of the PCM) the transmission to achieve maximum efficiency. The PCM regularly checks the voltage condition in the power relay control circuit that delivers battery voltage to the ECM/PCM.

How do you test if a relay is normally open?

Testing The Normally Open (NO) Terminal of The Relay

  1. Put the multimeter in the ohmmeter setting.
  2. Place one of the multimeter probes on the NO terminal and the other on the COM terminal.
  3. Read the resistance.
  4. If the resistance value is around several MΩ , the NO terminal is working fine.

How do you tell if relay is normally open or closed?

As relay diagrams show, when a relay contact is normally open (NO), there is an open contact when the relay is not energized. When a relay contact is Normally Closed (NC), there is a closed contact when the relay is not energized. In either case, applying electrical current to the contacts will change their state.

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How do you know if a PCM relay is bad?

Let’s get started!

  1. Your ‘Check Engine’ Light is On. …
  2. Your Car Won’t Start or Starts Roughly. …
  3. Sudden Loss of Gas Mileage. …
  4. You Failed Your Emissions Test. …
  5. Your Engine Stutters or Stalls. …
  6. Erratic or Random Shifting. …
  7. You’re Receiving a PCM-Related Error Code. …
  8. What to Do If You Experience PCM Failure Symptoms.

What is the difference between a PCM and a ECM?

The main difference between the two is that the ECM controls specific parts of the engine, regulating and sending commands. While the PCM is used in newer models to control almost all engine functions.

How do I fix code P068A?

How To Correct P068A ECM/PCM Power Relay De-Energized Performance – Too Early

  1. You must carefully repair and replace the alternator as well as its wiring and connectors.
  2. The defective ignition switch should be replaced properly.
  3. Make sure to replace the faulty PCM power relay.

What does a power relay do in a car?

Relays are switches controlled by electrical power, like another switch, computer or control module. The purpose of an automotive relay is to automate this power to switch electrical circuits on and off at particular times.

Which relay terminal is normally closed?

Relay Guide

Terminal/Pin number Connection
85 Coil
86 Coil
87 Normally Open (NO)
87a Normally Closed (NC) – not present on 4 pin relays

How do you open the relay on a wire normally?

Zitat von Youtube: These relays have power at the 87a. Terminal until the coils energized. When the relay is powered it switches the power to the 87 terminal and the 87 a terminal will then lose its power.

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