XJ XJ8 / XJR ( X308 ) 1997 - 2003

'00 Vanden Plas - Code 1631

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Old 06-17-2022, 07:15 AM
Djmcmann's Avatar
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Default '00 Vanden Plas - Code 1631

To all - first of all to those that answered my Vacuum Leak Question yesterday - thank you - however, I did not have a chance yet to do what you all recommended. In the meantime, I got a new issue, the car has been driving great and I took it out at lunch yesterday - no issues. When I went to go home, it started up and ran rough and the dashboard was like Christmas lights - the big issue is I am now getting the Engine Failsafe Mode.

When I got it home, I fully charged the battery which is about 1.5 years old but it was showing good when I started the charge. I let it charge over night and started it up and still the same issue.

So I am not sure what kicked it into getting this code and message. Below is a picture from my reader.

Any help or suggestions is apprreciated.



 
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Old 06-17-2022, 09:37 AM
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Some info for you.

P1631
Throttle motor power relay coil
activation circuit failure

Default Action
When RED MIL is activated
(DTC logged; first trip), ECM:
– Switches off throttle motor
(via relay)
– Initiates throttle “limp home”
mode: engine speed controlled to
between 1000-1250 rpm by fuel
cutoff to cylinders
– Inhibits idle speed control
– Inhibits cruise control
– Inhibits traction

Possible Causes
Throttle motor relay coil to ECM circuit
open circuit, short circuit to ground or
short circuit to B+ voltage
ECM failure
 
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  #3  
Old 06-18-2022, 08:19 AM
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Originally Posted by motorcarman
Some info for you.

P1631
Throttle motor power relay coil
activation circuit failure

Default Action
When RED MIL is activated
(DTC logged; first trip), ECM:
– Switches off throttle motor
(via relay)
– Initiates throttle “limp home”
mode: engine speed controlled to
between 1000-1250 rpm by fuel
cutoff to cylinders
– Inhibits idle speed control
– Inhibits cruise control
– Inhibits traction

Possible Causes
Throttle motor relay coil to ECM circuit
open circuit, short circuit to ground or
short circuit to B+ voltage
ECM failure
Hello, I had these codes a number of times on my first 2000 VDP. You can try removing the throttle position, throttle motor, and pedal position sensors and spraying them with contact cleaner and see if that gets the car going again. Chased this problem until I finally replaced the pedal position connector. I had replaced the throttle position connector as well. I replaced the throttle body before finally changing the connectors. It really could be any of those things; including needing to get a replacement throttle body.
I keep a battery disconnect on all my cars since that time....these cars are so sensitive to electrical problems it's just easier than keeping a 10mm wrench in the trunk!
 
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