How to bypass security P1638 - 2002 Jaguar X-Type

DTC P1638
The powertrain control module (PCM) uses the generator field duty cycle signal circuit to monitor the duty cycle of the generator. The generator field duty cycle signal circuit connects to the high side of the field winding in the generator. A pulse width modulated (PWM) high side driver in the voltage regulator turns the field winding ON and OFF. The PCM uses the PWM signal input to determine the generator load on the engine. This allows the PCM to adjust the idle speed to compensate for high electrical loads.
The PCM monitors the state of the generator field duty cycle signal circuit. When the key is in the RUN position and the engine is OFF, the PCM should detect a duty cycle near 0 percent. However, when the engine is running, the duty cycle should be between 5-100 percent. The PCM monitors the PWM signal using a key ON test and a RUN test. During the tests, if the PCM detects an out of range PWM signal, DTC P1638 will set. When the DTC sets, the PCM will send a class 2 serial data message to the IPC to illuminate the charge indicator.

Diagnostic Aids
• DTCs P1637 and P1638 may set at the same time depending on the failure.
• Use a scan tool in order to diagnosis the generator circuits. The scan tool should display Inactive for the L terminal and 10-40 percent for the F terminal when the ignition is ON. When the engine is operating, the display should indicate that the L terminal is Active and the F terminal is more than 10 percent.
• A generator fault, such as a shorted output diode, malfunctioning regulator, open or shorted rotor, or open sense lead or battery feed may cause a low battery charge. Refer to Charging System Test for further information and generator diagnosis.

You can't bypass it. It is security. Either the cluster , ECM or bad data wires is the problem.

They are manufactures codes,not generic

Without a factory work shop manual &
emission & diagnostic manuals,which
you need to buy & have, to work on your
own vehicles

Your left with the choice of a repair shop or dealer

P1638 Instrument to ECM , CAN (control area network) short circuit failure,this is either the instrument panel at fault or the ECM.Basically its a open wire. between ECM and instrument panel

CODE P1637 - GENERATOR L TERMINAL CIRCUIT MALFUNCTION CONDITIONS. CODE P1638 - GENERATOR F TERMINAL CIRCUIT MALFUNCTION CONDITIONS. POSSIBLE CAUSES FAULTY GENERATOR WHICH IS ALTERNATOR.CHECK GENERATOR POWER FEED WIRES AND CHECK GENERATOR VOLTAGE REGULATOR WIRES FOR LOOSENESS AND DAMAGE. MAKE SURE BATTERY VOLTS ARE 12.6 VOLTS. IF BATTERY WEAK DUE BAD GENERATOR VECHICLE WONT START.

Fault codes are listed in the technical handbook, no good to you as it's a Jaguar service item unless you can get a copy of JTIS from ebay etc.


Fault Code:- P1638 Indicates a Power-train fault


The fault is generally due to a problem in the Computer & Output Circuit area


Fault Description: CAN ECM / INST network malfunction

Action of ECM:- none


After clearing the DTC, complete the Ignition ON 10 seconds
Check for a reoccurrence of fault DTC.

Possible Fault:- CAN open circuit fault - INST to ECM CAN short circuit fault INST failure ECM failure D

http://newrockies.com/passkey They sell a bypass for your 95 regal factory security system.
On the left side of the site it says. PRO VATS full bypass. Thats the thing you need to bypass the factory security system.

If you have the chip in the key, this is the method I used for bypassing the entire security system and never heard about it anymore: http://newrockies.ca/vatsbypass