Technical Description of OBD-II Trouble Code
The circuit for controlling the intake valve solenoid is registering a high voltage (Bank 1).
What does that mean?
This code is a generic OBD-II powertrain code that applies to all vehicles (1996-newer), regardless of make and model. However, the specific repair steps may vary depending on the vehicle model.
In vehicles with variable valve timing (VVT), the Engine Control Module / Powertrain Control Module (ECM/PCM) regulates the camshaft position by controlling the engine oil flow through the control solenoid. The control solenoid is activated by a Pulse Width Modulated signal (PWM) from the ECM/PCM. If the voltage of this signal exceeds the specified range, the ECM/PCM will set this trouble code and activate the Malfunction Indicator Lamp (MIL).
Bank 1 refers to the side of the engine where cylinder #1 is located. It is important to verify this according to the manufacturer’s specifications. The intake valve control solenoid is typically situated on the intake manifold side of the cylinder head. This code is similar to codes P0075 and P0076 and may also be accompanied by P0026.
Symptoms
The symptoms may include:
Potential Causes
The potential causes of a P0077 diagnostic trouble code may include:
Diagnostic Steps
Wire harness – Check for unplugged harness connections, look for corrosion or loose wires to connectors. Unplug harness connectors from the solenoid and PCM. Using a wiring diagram, locate the positive (+) and negative (-) wires connected to the solenoid. The solenoid can be either ground side or power side controlled, depending on the application. Consult the factory wiring diagrams to determine the power flow in the circuit. Using a digital volt ohm meter (DVOM) set to the ohms setting, check for resistance between each end of the wire. An over limit reading on the DVOM may indicate an open in the wiring, loose connection, or terminal issue.
Control solenoid – With the electrical harness to the solenoid unplugged, use the DVOM set to ohms to check for resistance between each of the electrical terminals on the control solenoid itself. Refer to the factory specifications or use a known good control solenoid, if available, to determine if there is resistance in the solenoid. If the DVOM shows an over limit or very low resistance reading, the solenoid is likely faulty.
Short to power – Unplug the harness to the PCM/ECM and locate the wires connected to the control solenoid. With the DVOM set to the volts scale, connect the negative lead to ground and the positive lead to the wire(s) connected to the control solenoid. Check for voltage. If voltage is present, there may be a short to power in the wiring harness. Locate the short to power by unplugging harness connectors and testing the wiring back to the solenoid.
PCM / ECM – If all wiring and the control solenoid check out okay, it will be necessary to monitor the solenoid during engine operation by back probing the wires at the PCM/ECM. Use an advanced scan tool that can read the engine functions to monitor the duty cycle commanded to the control solenoid. It will be necessary to monitor the solenoid during engine operation under various engine RPMs and load conditions. Use an oscilloscope or graphing multimeter set to the duty cycle scale, connect the negative lead to a known good ground and the positive lead to either wire terminal at the solenoid itself. The reading on the multimeter tool should match the commanded duty cycle on the scan tool. If they are opposite, the polarity may be reversed. Connect the positive lead to the other wire terminal on the solenoid and re-test to verify. If the signal detected from the PCM is constantly on, there may be a fault with the PCM itself.
