P0078 B1 Exhaust Valve Control Solenoid Valve Circuit

P0078 B1 Exhaust Valve Control Solenoid Valve Circuit

OBD-II DTC Datasheet

Exhaust Valve Control Solenoid Circuit (Bank 1)

What does this mean?

This code is a generic OBD-II powertrain code, which means it applies to all makes and models of vehicles (1996 and newer), although specific repair steps may differ depending on the model.

On vehicles equipped with a variable valve timing (VVT) system, the engine control module / powertrain control module (ECM / PCM) monitors the camshaft position by adjusting the engine oil level with the camshaft position control solenoid. The control solenoid is controlled by a pulse width modulated (PWM) signal from the ECM / PCM. The ECM / PCM monitors this signal and if the voltage is out of specification or unstable, it sets this DTC and turns on the Check Engine Light / Malfunction Indicator Lamp (CEL / MIL).

Bank 1 refers to the #1 cylinder side of the engine - be sure to check according to the manufacturer's specifications. The exhaust valve control solenoid is usually located on the exhaust manifold side of the cylinder head. This code is similar to codes P0079 and P0080. This code may also be accompanied by P0027.

symptoms

Symptoms may include:

• Check Engine Light (Malfunction Indicator Lamp) is on
• The car can suffer from poor acceleration and reduced fuel consumption.

Possible reasons

Possible causes of DTC P0078 may include:

• Poor wiring harness connection or corroded terminals
• Defective control solenoid
• Short circuit to power
• Short circuit to ground
• Defective ECM

Diagnostic steps

Wiring Harness - Check for loose wiring harness connections, look for corrosion or loose wires to connectors. Disconnect the harness connectors from the solenoid and PCM using the wiring diagram, locate the + and - wires to the solenoid. The solenoid can be driven from the ground side or from the power side, depending on the application. Refer to the factory wiring diagrams to determine the power flow in the circuit. Using a digital volt/ohmmeter (DVOM) set to the Ohm setting, check the resistance between each end of the wire. Exceeding the limit on the DVOM could be an open in the wiring, a loose connection, or a terminal. The resistance should be around 1 ohm or less, if the resistance is too high, there may be corrosion or poor wiring between the solenoid and the PCM/ECM.

Control Solenoid - With the electrical harness disconnected from the solenoid, using the DVOM set to ohms, check the resistance between each of the electrical terminals on the control solenoid itself. Use factory specifications or a known-good control solenoid, if available, to determine if there is excessive resistance in the solenoid. If there is over limit or excessive resistance on the DVOM, the solenoid is probably bad. Test for a short to ground across the control solenoid by connecting one lead of the DVOM to a known good ground and the other to each terminal on the control solenoid. If resistance is present, the solenoid may have an internal short circuit.

Short to power - Disconnect the harness from the PCM/ECM and locate the wires to the control solenoid. With the DVOM set to volts, connect the negative lead to ground and the positive lead to the wire(s) to the control solenoid. Check for voltage, if present, there may be a short to power in the wiring harness. Locate a short to power by unplugging the harness connectors and checking the wiring back to the solenoid.

Short to ground - Disconnect the harness from the PCM/ECM and locate the wires to the control solenoid. With the DVOM set to volts, connect the positive lead to a known good voltage source, such as a battery, and the negative lead to the wire(s) to the control solenoid. Check for voltage, if present, there may be a short to ground in the wiring harness. Locate a short to ground by unplugging the harness connectors and checking the wiring back to the solenoid. Check for a short to ground through the control solenoid by connecting one lead of the DVOM to a known good ground and the other to each terminal on the control solenoid. If the resistance is low, the solenoid may be shorted internally.

PCM/ECM - If all wiring and control solenoid are OK, it will be necessary to monitor the solenoid while the engine is running by checking the wires to the PCM/ECM. Using an advanced scan tool that reads engine functions, monitor the duty cycle set by the control solenoid. It will be necessary to control the solenoid while the engine is running at various engine speeds and loads. Using an oscilloscope or graphical multimeter set to duty cycle, connect the negative wire to a known good ground and the positive wire to any wire terminal on the solenoid itself. The multimeter reading should match the specified duty cycle on the scan tool. If they are opposite, the polarity may be reversed - connect the positive wire on the other end of the wire to the solenoid and repeat the test to check. If no signal is found from the PCM, the PCM itself may be faulty.

Related DTC discussions

• P0014 / p0078Camshaft timing control solenoid valve B1. Exhaust Valve Control Solenoid Circuit Block 1. I replaced the solenoid with a new one, but I have 2 of them, so I don't know if I did the wrong one. I read that it could be a wiring harness. I do not know what to do at this moment…. 
• Nissa Versa 2013 - Exhaust Solenoid - Error Code P0078Hello forum, Happy New Year ..! I need help locating an exhaust VVT solenoid sensor in a 2013 Nissan Versa Sedan SV. My engineer does not work well, he does not accelerate and I need to accelerate more to reach my speed, as well as poor gasoline performance. The gear does not shift at all ... 

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