Camshaft Position Sensor A Circuit Low Input (Bank 1)
Note: The “A” identifies the intake camshaft, which is located to the intake side of the cylinder head. “Bank 1” denotes the engine bank that contains the number one cylinder.
The PCM has detected an incorrect voltage reading or waveform from the camshaft position sensor circuit for camshaft sensor “A” in engine bank 1. The camshaft position sensor is a stationary electro-magnetic sensor that works in conjunction with teeth or notches on the camshaft. The teeth or notches on the camshaft interrupt the sensor’s magnetic field (as perceived by the PCM) to input camshaft position data. This data is used in calculating fuel delivery and ignition timing.
Code Set Parameters
Deviations in system reference voltage, that exceed 10-percent of the manufacturer’s specified reference value may cause a code to be stored and a malfunction indicator lamp to be illuminated. These deviations are perceived by the PCM as incorrect camshaft position. Some vehicles will store a code and illuminate a service engine soon lamp on the first drive cycle and others require multiple drive cycles (usually three) for a service engine soon lamp to be illuminated. Nevertheless, a code should be stored on the same drive cycle in which the initial failure has occurred.
Some symptoms that accompany this code may include delayed engine starting, a rough idling engine, choppy or hesitant acceleration, a no start condition, or an overall lack of engine performance.
The most common cause of this code is related to oil (or other engine fluids) that have leaked onto sensors, wiring, or electrical connectors. This typically causes grounded, broken, or shorted wiring, along with loose or shorted electrical connectors. In some cases fluid contamination has also caused camshaft sensors to go bad. Some vehicles will store a camshaft position sensor circuit code if the crankshaft sensor goes bad. If one or the other is found to be faulty; it is recommended that camshaft and crankshaft sensors be replaced as a set. PCM failure is also possible but rarely occurs.
My most frustrating misdiagnosis comes from a faulty replacement sensor. OEM quality components fail far less frequently than “bargain basement” parts. Just because something is dirt cheap doesn’t mean that it is a bargain. This code pertains to the entire camshaft position sensor circuit. Do not condemn the sensor before performing a thorough diagnosis of the entire system.
- The camshaft position sensor is an electro-magnetic sensor that interacts with a metal reluctor ring (or gear) on one end or the other of the camshaft
- Engines that utilize multiple camshafts (dual-overhead cam engines) are equipped with multiple camshaft position sensors
- As the reluctor passes by the sensor, a precisely placed hole or gap in the teeth interrupts the waveform pattern sent by the sensor to the PCM
- This interruption correlates with an ignition timing reference value that is programmed into the PCM
- Variations from the manufacturer’s reference timing value (seen as voltage waveforms) will cause a code to be stored and possibly a malfunction indicator lamp to be illuminated.
Several specialty tools will be required to diagnose this code successfully
- They include a scanner, a digital volt/ohmmeter, and possibly an oscilloscope.
Begin with a visual inspection of all wiring and connectors
- Repair or replace damaged, disconnected, shorted, or corroded wiring, connectors, and components as necessary
- Always retest the system after repairs are completed to ensure success.
If all system wiring, connectors, and components (Including fuses) appear to be in normal working order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes and freeze frame data
- This information can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored
- Continue by clearing the code and operating the vehicle to see if it returns
- This will help to determine whether or not the malfunction is intermittent
After the codes are cleared, test drive the vehicle to see if the code returns
- If the code fails to immediately return, you may have an intermittent condition
- 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
- In the event of an intermittent condition, you may also utilize the oscilloscope to monitor waveforms created by the distributor, camshaft, and/or crankshaft sensor/s, while looking for glitches or other inconsistencies.
Suspect areas of system circuitry that are contaminated with oil, antifreeze, or power steering fluid that has leaked from the engine
- If wiring with missing or distorted insulation is found, repair or replace it as necessary.
If no obvious system circuitry problems are discovered, perform a resistance test at the camshaft position sensor and a voltage test on the sensor connector
- Using your digital volt/ohmmeter test reference voltage at the camshaft position sensor and compare your findings with the manufacturer’s specified reference voltage
- If system reference voltage readings are in line with specified values (or if sensor resistance values do not coincide), replace the camshaft sensor and crankshaft sensor.
If system voltage readings do not coincide with manufacturer’s specified reference figures, check system continuity using your digital volt/ohmmeter
- Use caution when checking resistance values in wiring that is connected to the PCM
- For best results, disconnect the electrical connector from the PCM prior to using an ohmmeter on the harness side of the circuit
Remember that PCM failure is possible but very rare