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Error Code P1626 is defined as Theft Deterrent Fuel Enable Signal Not Received.
This error code is a manufacturer-specific trouble code, meaning it does not apply to all vehicles makes. Rather, it applies only to specific vehicle makes, such as Chevrolet. Specification on the definition, troubleshooting, and repairs still vary from one make and model to another.
The VTD (Vehicle Theft Deterrent) system is included in the vehicle’s BCM (Body Control Module). The PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) monitors the state of serial data message coming from the VTD, ensuring the communication between the PCM and BCM is established. If the PCM detects a loss of state of the signal while the engine is running, then the Error Code P1626 will be set.
This error code will keep the vehicle from starting, or cause problems in the normal operation depending on when the loss of communication was detected. The engine will continue to start and run if the condition that set the code happened after the PCM received a valid theft deterrent password XXXXX the BCM and already allowed fuel to the ignition cycle. If the condition that set the code occurred before the PCM received a valid theft deterrent password, then the engine will start and stall immediately. Having this condition, the PCM will inhibit fuel delivery, disable the starter unit a valid theft deterrent password XXXXX XXXXX. You can refer to the VTD Circuit Description in Theft Deterrent part of your manual.
As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s system. Also, since it’s a theft deterrent code, it will keep the car from running by refusing to start.
There are more than a couple of possible causes for this error code to appear, including:
- Defective ignition switch
- Open or shorted ignition switch harness
- Poor electrical connection in ignition switch harness
- Use of wrong ignition key
How to Check
To diagnose this error code, you need to hook up a scanner and see if the key is being recognized by the PCM. This might be in the engine section of the scanner of the BCM. If the key is not there, the fuel will shut off, and the engine will start and die. Other cars work the same way, such as Volvo. To check further, try these:
Test the Passlock sensor circuit voltage located at the sensor connector terminal. Yellow wire signal 5V disconnected, terminal B Black wire ground, terminal C White wire 12V.
Then, test the Passlock sensor signal back probed at the Yellow wire voltage from the lock, through the crank, and to the run position.
Repeat the test during start and run, and start and stall.
If the signal voltage is in a consistent sequence when you do a start and run and when start and stall, that means the BCM may be failing. The BCM must be Electrically Erasable Programmable Read Only Memory (EEPROM) programmed, then Regular Production Option (RPO) configured and then conduct a Passlock system learn.
Next, make sure the PCM maintains a good power and ground. It may be having an intermittent drop out caused by the bad ignition switch. If this is the case, you must monitor voltages when the stall occurs, or when the Error Code P1626 sets.
If the signal voltage is in an inconsistent sequence, verify the 12V and ground circuits. If you’re not getting the right reading, that means you need to replace the Passlock sensor/ignition switch.
How to Fix
Repair or replace shorted ignition switch harness
Repair or replace the poor electrical connection in ignition switch harness
Replace the Passlock sensor/ignition switch
This code can be easy to fix, just make sure you go through the step by step diagnosis thoroughly.