What does it mean?
OBD II fault code B1600 is a manufacturer specific code that is defined by car maker Ford as “PATS Ignition Key Transponder Signal Is Not Received”, or sometimes as “No PATS Key Read by the PATS Control”, and is set when the PCM (Powertrain Control Module) detects a communication failure between a PATS key and the PCM/Immobilizer. Note that the word “PATS” refers to the P assive A nti- t heft S ystem on Ford products.
NOTE: Code B1600 is also used by General Motors, who defines it as “LF (Left Front) mirror motor #1 (single motor or vertical) circuit malfunction” On Ford applications, the operation of the PATS system depends on the PCM being able to read the security code that is encrypted into a compatible PATS ignition key. Note that unlike similar systems on other vehicle brands, the encryption on Ford PATS key is stored on a chip within the key that does not require a power source to function.
In terms of operating principles, when a PATS key is inserted into the ignition switch and turned to either the “ON” or “START” position, the PCM sends a signal to the PATS transceiver, which initiates a process of communication with the key .
This process establishes a link with the transponder in the key in order to read the encrypted security code that is stored in the key; the retrieved code is then sent to the PCM, which then compares the obtained code with the codes that is stored in a dedicated part of its memory. If the code that was retrieved from the key matches one of the codes stored in the PCM, it will ground the starter motor solenoid and enable the fuel injectors, thus enabling the engine to start.
If however, the retrieved code does not match one of the codes stored in the PCM, the PCM will not ground the starter motor solenoid and enable the fuel injectors, thereby effectively preventing the engine from starting. However, even if the retrieved security code does match a code stored in the PCM, but the PCM detects a failure, malfunction, defect, or abnormal voltage anywhere in the PATS system, the PCM will not ground the starter motor or enable the fuel injectors.
Since the PCM cannot always distinguish between genuine failures or defects and attempts to tamper with the PATS system, keeping the starter motor and fuel injectors disabled is a default reaction when one or more parts of the PATS system does not work as expected.
Nonetheless, when the PCM detects either a PATS key code that does not match a stored code, or any defect, failure, malfunction or abnormal voltage anywhere in the PATS system it will disable both the starter motor and the fuel injectors, in addition to setting one or more trouble codes and illuminating a warning light.
Symptoms
- Engine cranks normally but will not start, or fires for a second and dies
- Theft or security indicator flashes rapidly or stays lit instead of its normal brief self-check
- The spare key starts the vehicle while the everyday key does not, or the fault comes and goes with key position
- No start immediately after fitting an aftermarket alarm, remote starter or a newly cut key
- No fuel pressure build-up on cranking because the injectors stay disabled
- On the mirror motor variant, the left mirror does not move in one axis
Likely causes
- A key without a working transponder chip: a plain mechanical copy, a valet key, or a chip damaged by impact
- Two chipped keys or an extra transponder tag on the same ring, so the antenna ring cannot read a single clear code
- Transceiver antenna ring around the ignition lock damaged, unplugged, or with a broken connector tab
- Open, chafed or corroded wiring between the antenna ring and the control module
- Electrical interference near the ignition lock from an aftermarket alarm, remote starter, phone holder or magnetic accessory
- Low battery voltage or heavy voltage drop during cranking, which corrupts the transponder read
- Failed control module, or key programming lost after a module replacement or reflash
- On some applications this code number is assigned instead to the left front mirror motor circuit
How to fix it
- Try every known good key, and remove all other keys, tags and metal fobs from the ring before testing
- Note the theft indicator flash pattern and read any related security codes stored alongside this one
- Confirm battery condition and charging voltage, since a weak battery causes false transponder faults during cranking
- Inspect the transceiver ring at the ignition lock: check that the connector is latched, the wires are not broken where they leave the ring, and nothing was crushed during column work
- Measure supply and ground at the transceiver and check the signal wire to the module for an open or a short
- Remove any aftermarket alarm or remote start module mounted near the ignition lock and retest, as interference is a common cause
- Reprogram the keys with the correct security procedure, and replace the antenna ring or the key only after wiring and interference have been ruled out
- Where the code refers to the mirror motor, test the motor supply, ground and switch feeds instead