For Honda engine enthusiasts and mechanics working with OBD2 systems, particularly during engine swaps or modifications, encountering the need to bypass the crank sensor (CKF) is not uncommon. This guide explains a practical method to bypass the OBD2 crank sensor, drawing from community knowledge and focusing on clear, actionable steps.
In OBD2 Honda vehicles, the engine control unit (ECU) diligently monitors the relationship between the crankshaft position sensor (CKF) and the camshaft position sensor (CKP), typically located in the distributor. Both sensors generate signals – 12 pulses per crank revolution – which the ECU compares to ensure correct timing belt alignment. When the CKF sensor is removed, often during engine swaps or when using specific aftermarket setups, the ECU will detect a discrepancy and may trigger error codes or affect engine performance.
The bypass method leverages the existing CKP sensor signal from the distributor. By cleverly routing this signal to also serve as the CKF sensor input, we can satisfy the ECU’s monitoring requirements. Essentially, we are telling the ECU that both the crank and distributor sensors are providing synchronized signals, even though the physical CKF sensor is absent.
Here’s how to perform the Obd2 Crank Sensor Bypass:
For OBD2a Honda ECUs, the process involves manipulating specific pins. Locate pins C1 and C11, which are designated for the CKF sensor. These are typically found with pin 11 directly below pin 1. Carefully cut these wires a few inches away from the ECU connector. On the ECU connector side, tap wire C1 into pin C4, ensuring the original wire in pin C4 remains connected. Similarly, tap wire C11 into pin C14 (pin 14 is directly below C4), again making sure the original C14 wire stays connected. Effectively, pins C4 and C14 will now receive signals from both their original sources and the CKP sensor signal rerouted from where C1 and C11 were initially connected. The wires on the harness side of C1 and C11, which originally went to the now removed CKF sensor, can be left disconnected and properly insulated.
Important Note for OBD2b: The pin layout and wire colors can differ significantly for OBD2b ECUs compared to OBD2a. The pin assignments mentioned above are specific to OBD2a. If you are working with an OBD2b system, it is crucial to consult a reliable OBD2 pinout diagram specific to your vehicle and ECU to identify the correct CKF and CKP sensor pins. Incorrect wiring can lead to ECU damage or malfunction.
By implementing this OBD2 crank sensor bypass, you effectively provide the ECU with the necessary signal continuity, allowing your Honda engine to run smoothly even without the physical CKF sensor. Always double-check your wiring and consult vehicle-specific resources to ensure proper execution and avoid potential issues.
