|Code||Fault Location||Probable Cause|
|P0023|| Camshaft position (CMP) actuator, exhaust/right/rear, bank 2 -circuit malfunction |
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|Wiring, CMP actuator, ECM|
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What Does Code P0023 Mean?
Code P0023 is defined as “Camshaft position (CMP) actuator, exhaust/right/rear, bank 2 circuit malfunction”, and is set when a fault is detected in the electrical circuit that controls the variable valve/cam timing system. Code P0013 relates to the B, or exhaust camshaft on Bank 2, which is the set of cylinders opposite the side of an engine that contains cylinder #1.
The function of variable valve timing is to enable engines to develop more torque under different operating conditions. For instance, valve/cam timing can be retarded at high engine speeds to increase power output, and to reduce harmful exhaust emissions such as nitrous oxide. When the system advances valve/cam timing, fuel economy is improved under light engine loads.
In terms of the system’s operation, valve/cam timing is either advanced or retarded by the action of pressurized oil on a mechanism that forms part of the camshaft. Design specifics vary from system to system but in principle, the pressurized oil acts on an actuator to rotate the camshaft either clock-wise, or counter-clockwise relative to a base timing position to advance or retard the valve timing, depending on operating conditions such as varying loads on the engine, and throttle inputs from the driver.
The image below shows a typical oil flow control valve, with the solenoid and electrical connector making up the top part of the assembly. Note the fine wire mesh screens on the bottom part. These are essential to prevent solid particulate matter in the oil from interfering with the operation of the actuator on the camshaft.
Note: “Circuit Malfunction” indicates that there is a malfunction in the control circuit, as opposed to a fault in a sensor or other component. With “Circuit Malfunction” codes, replacement of sensors and components in the affected circuit will almost never resolve the problem, since as the code suggests, the trouble is in the circuit. This distinction between “circuit” and “sensor/component” is a great help to anyone trying to diagnose a circuit malfunction code, since it narrows the list of possible causes down considerably.
The causes of “Circuit Malfunction” codes are much the same as those for “Open Circuits” i.e., broken wiring, poor connections across electrical connectors or previously repaired wiring, loss of ground that prevents current flow, blown fuses, defective relays, faulty switches, or any of a host of other issues and problems that prevents a flow of current through wiring. Issues like high/low/intermittent voltages can set a “Circuit Malfunction” code on some applications. Moreover, “Circuit Malfunction” codes could also indicate a problem with negative current control / flow, as well as issues with failed or failing PCM’s (Powertrain Control Modules), although control module failure is a rare event.
What are the common causes of code P0023 ?
Common causes of code P0 023 include:
- Damaged, or malfunctioning ECM.
- Defective, or malfunctioning oil flow control valve control solenoid.
- Breaks in wiring causing loss of continuity, or intermittent loss of continuity.
What are the symptoms of code P0023 ?
Common symptoms of Code P0023 are:
- Illuminated check engine warning light.
- Rough running at high engine speeds.
- Loss of power at mid, and high range RPM’s.
- Increased fuel consumption.
- Occasional stalling, especially under hard acceleration.
- Occasional hard starting.
- In some cases, there may be no noticeable symptoms apart from the illuminated check engine light, especially at small throttle openings during reduced loads on the engine.
NOTE: Symptoms of Code P0023 are of little, or no use as diagnostic aids, since these symptoms can be caused by a myriad other, unrelated issues. At best, the above symptoms can be used as confirmation of a circuit failure in the variable valve/cam timing system.
How do you troubleshoot code P0023 ?
Troubleshooting Code P0023 involves a circuit check, and all diagnostic procedures must therefore include inspecting, and testing the wiring harness and control solenoid. The circuitry is relatively simple, consisting for the most part of a 12 volt DC power supply to the oil flow control valve, a ground pin to which the ECM supplies a ground at the correct time and in the correct amount, and a feedback loop to the ECM to confirm functionality.
Basic trouble shooting steps
- With the engine off, check the electrical connector on the oil flow control valve for signs of damage, looseness, and/or corrosion. Clean, replace, or repair connector as required.
Check for continuity in the wiring at the oil flow control valve. If continuity is interrupted, inspect wiring to trace breaks, and/or poor connections, and repair as required.
Check oil flow control valve solenoid resistance, and compare results with the value specified i the repair manual. Replace solenoid if resistance is out of spec.
With the engine off, remove the oil flow control valve solenoid, and apply power directly from the battery, but ensure a sound ground connection is made. Replace the solenoid if a direct power supply fails to activate the solenoid.
If a direct connection activates the solenoid, replace the solenoid, and inspect the wiring between the solenoid and the ECM for short circuits, open circuits, or high resistance. Repair as required.
If all wiring checks out OK, use a suitable scan tool to check the functioning of the oil flow control solenoid and valve. The valve should be closed during idling, but higher engine speeds will activate it. Check the status of the valve through the rev range of the engine to see if it changes from “OFF”, to “ON” as the engine speed changes. Replace the solenoid/valve if the status does not change.
In cases where the pulse width of the oil flow control valve is modulated, the active duty cycle should vary with engine speed. If this does not happen, the cause is almost certainly due to a defect or malfunction in the ECM.
In cases where the ECM delivers valid commands to the oil flow control valve, but the cam/valve timing does not return to the base timing, or where the cam phaser does not advance/retard timing sufficiently or correctly, there may be an intermittent fault in the control solenoid, or in the associated wiring. In these cases, it is advisable to replace both the oil flow control solenoid, and the entire harness that controls it. If the fault persists, have the ECM tested if possible, or replace the ECM.
Codes Related to P0023
Codes related to P0023 are:
- P0013: Relates to a circuit failure in the B (Exhaust) camshaft actuator on Bank 1.
- P0014: Relates to B (Exhaust) Camshaft Position, where the cam timing is over-advanced on Bank 1. This code could also be set as the result of a performance failure in the system.
- P0015: Relates to the B (Exhaust) cam timing being over-retarded on Bank 1.
- P0024: Relates to A (Exhaust) cam timing being over advanced on Bank 2. The code could also be set as the result of a performance failure in the system.
- P0025: Relates to A (Exhaust) cam timing being over-retarded on Bank 2.
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