P38 4.0 v8

Hi All, I have a strange fault on a 2000 plate 4.0 v8 sometimes it will start and other times not, I get a code which is p1667 any suggestions or point me in the right direction would be most appreciated.

SDA said:

Hi All, I have a strange fault on a 2000 plate 4.0 v8 sometimes it will start and other times not, I get a code which is p1667 any suggestions or point me in the right direction would be most appreciated.

Click to expand...

P1667 is "Engine Anti-theft signal circuit low, serial link short to earth".

AFAIK it generally means the engine ECU hasn't received a valid immobiliser code from the BECM. This can be due to a number of reasons...
1) it's gone out of sync (unlikely if it only does it sometimes)
2) the passive immobiliser is on and re-immobilising the vehicle after a 'time out' period and the key hasn't sent another unlock code to the BECM to re-mobilise the vehicle
3) there is a problem on that wire (also more unlikely, but not impossible!) which occasionally causes it to short out and the code isn't received properly.

The codes coming up don't always mean there is an issue or it's out of sync - the ECU will display that code at any time when it isn't currently receiving the code from the BECM.

Has anyone unplugged the RF receiver under the rear parcel shelf (driver's side)?

Thank you all for that info, time to get a wiring diagram out I think.

I would test the battery due to the low temperatures and Test alternator output, i've had many strange intermittent becm/locking faults due to this. (But not this one)
Corrosion on below carpet wiring and in connection blocks around becm especially on this old motor and following historic heater matrix o'ring failure.
Get a can of electrical contact cleaner and do all the blocks as you go.
Also, while lifting the carpet you may find enough loose change to cover the cost of the cleaner.
Good luck

resuscitating this old thread. I am now struck with a P1667 and a no start.
critical data:
- 2001 4.6 NAS P38 LHD
- Key fob arms and dis-arms the alarm and unlocks the doors as it should. Red light on dash is off when disarmed and blinking when armed.
- battery is low (11.95V)... lazy alternator will be replaced today. I disconnected the battery and will return in a couple of hours and use jumper cables from a 'charger car' when reconnecting. The intent here is to 'fool' the P38 into thinking it has a fresh battery. In fact the battery is fresh (just 2 months old Interstate "31 series") but clearly has not been receiving proper charge from alternator. I have noticed only12.8 -13V when running down the road and was about to replace the alternator anyway.
- I DO get RPM data from an OBD reader when cranking the engine (155-160 RPM). This may suggest crank pos sensor is functioning but not certain that is the source of the OBD data.
- This is a VERY sudden change. Car was in a parking garage...attendants brought it to the front without incident.... when we arrived 15 mins later it would not start.

I would suggest that the battery held just enough power to allow the first start but with no running time the alternator couldn't replenish it.

Indeed. It is my fault that I did not monitor alternator output until it was too late and the time ran out.

Any suggestions? Would a trickle charger refresh it to the point of decent health? And is it a high confidence that a properly powerful battery will solve the problem?

WaltNYC said:

Indeed. It is my fault that I did not monitor alternator output until it was too late and the time ran out.

Any suggestions? Would a trickle charger refresh it to the point of decent health? And is it a high confidence that a properly powerful battery will solve the problem?

Click to expand...

1 possibly and 2 yes.but check the alternator output.

New battery and same result. I suppose I am needing a re-sync.