P1646 - 2001 XJ Sovereign - HELP...
#1
P1646 - 2001 XJ Sovereign - HELP...
I have just gotten the CEL on and did a check for the fault code but no message and did a fault code check.
It came up with P1646. I erased it, but it comes up again after the next drive, so it seems valid.
The JTIS tells me this:
EOBD
P1646
FAULT DESCRIPTION
EOBD Fuel pump 2 (SC) relay malfunction
MONITORING CONDITIONS
Ignition ON > 5 seconds
DEFAULT ACTION
When fault is detected, ECM:
– Limits engine speed to
3000 rpm
POSSIBLE CAUSES
Fuel pump relay 2 failure
Fuel pump relay 2 to ECM circuit fault
Fuel pump relay 2 coil power supply open circuit
ECM ground circuit fault (relay coil drive
This is about where my knowledge stops and I need a bit of help to continue so that I can fix this.
Is it as simple as changing the Fuel pump relay or what do I need to do?
The car runs pretty OK, but it sometimes feels as if the engine is running a bit rough. Mostly on longer drives.
Thank a lot in advance
Thomas
It came up with P1646. I erased it, but it comes up again after the next drive, so it seems valid.
The JTIS tells me this:
EOBD
P1646
FAULT DESCRIPTION
EOBD Fuel pump 2 (SC) relay malfunction
MONITORING CONDITIONS
Ignition ON > 5 seconds
DEFAULT ACTION
When fault is detected, ECM:
– Limits engine speed to
3000 rpm
POSSIBLE CAUSES
Fuel pump relay 2 failure
Fuel pump relay 2 to ECM circuit fault
Fuel pump relay 2 coil power supply open circuit
ECM ground circuit fault (relay coil drive
This is about where my knowledge stops and I need a bit of help to continue so that I can fix this.
Is it as simple as changing the Fuel pump relay or what do I need to do?
The car runs pretty OK, but it sometimes feels as if the engine is running a bit rough. Mostly on longer drives.
Thank a lot in advance
Thomas
#2
#3
I think you may have the wrong code definition there. P1646 on AJ27 '99 on is "ECM HO2S control malfunction – B bank, upstream". You have a possible defective pre-cat O2 sensor is all. P1646 as a fuel pump relay error is from older (e.g. '95) regular XJ - suggest you check your JTIS again.
Jim
Jim
Last edited by jima; 03-05-2010 at 04:41 PM.
#4
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#8
It sounds like your car is not supercharged. That would be why you do not have the fuel pump 2 relay. That code is a problem as someone else mentioned. They used it for 2 totally different things, fuel pump fault and O2 sensor fault. If your car is not supercharged I would check the fuse and relay for the O2 heater circuit. If the fuse and relay check ok check for 12 volts and ground at the O2 sensor connectors heater wires. If you have power and ground you could replace the bank 1 sensor as a guess without further diagnosis but they are expensive. Proper diagnosis would require monitoring the O2 sensor output on a fast volt meter or oscilloscope.
#9
It is down as a CK2 which means it needs the error on 2 consecutive trips before it will throw a CEL and a P1646. Is the (SC) reference in the message to "SuperCharged" - can someone confirm?
Jim
Stop press: just read Real_Tech's post - if you have a sniff of a suspicion it might be O2 sensor related after all, swap over the left and right bank sensors if the wires will reach - the P1646 will change to a P1647 if it is O2 sensors.
Last edited by jima; 03-06-2010 at 09:47 AM.
#10
#11
Yes it does, definitely the Fuel Pump 2 Relay message. My error, not O2 sensors at all (I'm sensitive to them as both mine had to be replaced and P1646/P1647 is burned into my brain). Wish they wouldn't keep re-using the codes for other things on later models. Hey ho!
It is down as a CK2 which means it needs the error on 2 consecutive trips before it will throw a CEL and a P1646. Is the (SC) reference in the message to "SuperCharged" - can someone confirm?
Jim
Stop press: just read Real_Tech's post - if you have a sniff of a suspicion it might be O2 sensor related after all, swap over the left and right bank sensors if the wires will reach - the P1646 will change to a P1647 if it is O2 sensors.
It is down as a CK2 which means it needs the error on 2 consecutive trips before it will throw a CEL and a P1646. Is the (SC) reference in the message to "SuperCharged" - can someone confirm?
Jim
Stop press: just read Real_Tech's post - if you have a sniff of a suspicion it might be O2 sensor related after all, swap over the left and right bank sensors if the wires will reach - the P1646 will change to a P1647 if it is O2 sensors.
#12
Jim
#13
yep. I dunno. The wideband sensors theoretically happened in '99, I believe. I don't have access to the parts list, so I am not sure.
WILD GUESSES??- Wrong data in JTIS, replaced ecu?
Since it is NA, AND it did noit have the pump2 relay, I would have to believe it is certainly not a fuel pump problem. AS yiu said, sure wish they didn't reuse codes.
WILD GUESSES??- Wrong data in JTIS, replaced ecu?
Since it is NA, AND it did noit have the pump2 relay, I would have to believe it is certainly not a fuel pump problem. AS yiu said, sure wish they didn't reuse codes.
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