CAL Key Programming and Remotes 2 — Questions and Answers
Question 1: What is the primary difference between a transponder key and a proximity (PEPS) key?
- Transponder keys use passive RF; PEPS keys require active battery-powered transmission at close range
- Transponder keys require the ignition to be on before communicating; PEPS keys communicate while the ignition is off
- Transponder keys contain a glass-encapsulated chip that responds to exciter coil energy; PEPS keys use active RF for push-button start without inserting the key (Correct answer)
- Transponder keys are only used on domestic vehicles; PEPS keys are only used on imports
Correct answer: Transponder keys contain a glass-encapsulated chip that responds to exciter coil energy; PEPS keys use active RF for push-button start without inserting the key
Transponder keys house a passive chip energized by the ignition coil ring, while PEPS (Passive Entry/Passive Start) keys transmit actively so the vehicle can be unlocked and started without inserting the key.
Question 2: When performing an OBD-II key programming procedure, which tool interface is most commonly used to communicate with the vehicle's BCM or IMMO module?
- Serial RS-232 port
- OBD-II DLC (Data Link Connector) with J1850 or CAN protocol (Correct answer)
- Infrared (IR) port near the rearview mirror
- 30-pin diagnostic connector under the hood
Correct answer: OBD-II DLC (Data Link Connector) with J1850 or CAN protocol
The OBD-II DLC, located under the dash, uses protocols like CAN Bus or J1850 to allow programming tools to communicate with the immobilizer or BCM.
Question 3: A technician is programming a new remote key fob but the vehicle only accepts one key during the programming session. What is the most likely cause?
- The vehicle's battery voltage is too low
- The vehicle uses a 'dealer-only' programming mode that locks out additional keys
- The EEPROM on the key fob is corrupted
- The vehicle has already reached its maximum stored key limit (Correct answer)
Correct answer: The vehicle has already reached its maximum stored key limit
Most vehicle immobilizer systems have a finite limit (commonly 4–8 keys); once that limit is reached, no additional keys can be programmed without deleting existing ones.
Question 4: What does 'key learning' via EEPROM mean in automotive locksmithing?
- Programming the key through the OBD port using dealer software
- Reading and writing the immobilizer's secret data directly from the ECU chip to clone or add a key (Correct answer)
- Teaching the remote to operate the power windows
- Copying the mechanical key cut using a code machine
Correct answer: Reading and writing the immobilizer's secret data directly from the ECU chip to clone or add a key
EEPROM-based key learning involves physically reading the immobilizer data from the ECU chip (often soldered on the board) and writing a new key's crypto token directly into that memory.
Question 5: Which frequency is most commonly used by North American OEM remote keyless entry (RKE) systems?
- 315 MHz (Correct answer)
- 433.92 MHz
- 868 MHz
- 125 kHz
Correct answer: 315 MHz
315 MHz is the standard frequency for most North American OEM RKE fobs, while 433.92 MHz is more common in European and Asian markets.
Question 6: A 2018 Ford F-150 requires a new transponder key. The technician finds the vehicle is equipped with the PATS (Passive Anti-Theft System). Which chip type does PATS most commonly use?
- Texas Instruments DST80
- Megamos 48
- Texas Instruments 4D/80-bit (Correct answer)
- Philips/NXP PCF7935
Correct answer: Texas Instruments 4D/80-bit
Ford PATS systems on late-model F-150s commonly use Texas Instruments 4D or 80-bit transponder chips for encrypted immobilizer communication.
Question 7: When synchronizing a remote key fob that has fallen out of sync with the vehicle, what is the recommended first step?
- Replace the fob battery and attempt re-sync using the vehicle's built-in programming mode (Correct answer)
- Reprogram the fob's rolling code by connecting it to an EEPROM reader
- Replace the remote entirely as rolling codes cannot be reset
- Perform an OBD reflash to reset the Body Control Module
Correct answer: Replace the fob battery and attempt re-sync using the vehicle's built-in programming mode
A weak or dead battery is the most common cause of sync loss; replacing it and running the vehicle's onboard programming sequence often restores communication.
CAL Key Programming and Remotes 2
What is the primary difference between a transponder key and a proximity (PEPS) key?