2001 Jeep Cherokee check engine light

[drpaul87]

Hopefully someone knowledgeable can help. I had my check engine light come on, and the Jeep runs fine. Took it to Auto Zone to be scanned. Code P01494. Worker there says it is the valve on the evap. cannister. First off, how do I check it? Second...could a mis start cause it?(I was cranking to start and let go of the key that split second before it started...resulting in what sounded like a backfire)
Thank you to any and all that can help.

[c180]

Symptom:
P1494-LEAK DETECTION PUMP SW OR MECHANICAL FAULT
When Monitored and Set Condition:
P1494-LEAK DETECTION PUMP SW OR MECHANICAL FAULT
When Monitored: Immediately after a cold start, with battery/ambient temperature
between 40 deg. F and 90 deg. F and coolant temperature within 10 deg. F of battery/
ambient.
Set Condition: The state of the switch does not change when the solenoid is energized.
POSSIBLE CAUSES
WIRING HARNESS INTERMITTENT
LDP SWITCH SENSE CIRCUIT SHORTED TO GROUND
LDP VACUUM SUPPLY
LEAK DETECTION PUMP
LDP SWITCH SENSE CIRCUIT OPEN
POWERTRAIN CONTROL MODULE
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, read DTC’s.
Is the DTC Good Trip Counter displayed and equal to zero for P-1494?
All
Yes ® Go To 2
No ® Go To 7
2 Turn the ignition off.
Disconnect the vacuum supply hose at the Leak Detection Pump.
Connect a vacuum gauge to the disconnected vacuum supply hose at the Leak
Detection Pump.
Start the engine and read the vacuum gauge.
Does the vacuum gauge read at least 13 in/Hg?
All
Yes ® Go To 3
No ® Repair leak or obstruction in vacuum hose as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 6.
176
DRIVEABILITY - GAS
TEST ACTION APPLICABILITY
3 Turn the ignition off.
Disconnect the Leak Detection Pump harness connector.
Disconnect the PCM harness connector(s).
Note: Check connectors - Clean/repair as necessary.
Measure the resistance of the LDP Switch Sense Circuit from the PCM harness
connector to LDP harness connector.
Is the resistance below 5.0 ohms?
All
Yes ® Go To 4
No ® Repair the open Leak Detection Pump Switch Sense Circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 6.
4 Turn the ignition off.
Disconnect the Leak Detection Pump electrical harness connector.
Turn the ignition on.
With the DRBIIIt in Inputs/Outputs, read the 9Leak Detect Pump Sw9 state.
While observing the 9Leak Detect Pump Sw9 state, connect a jumper wire between a
good 12 volt source (B+) and the LDP Switch Sense circuit.
Did the 9Leak Detect Pump Sw9 state change when the jumper was connected?
All
Yes ® Replace the Leak Detection Pump.
Perform POWERTRAIN VERIFICATION TEST VER - 6.
No ® Go To 5
5 Turn the ignition off.
Disconnect the Leak Detection Pump electrical harness connector.
Disconnect the PCM harness connector(s).
Measure the resistance between the LDP Switch Sense circuit and ground.
Is the resistance below 5.0 Ohms?
All
Yes ® Repair the LDP Switch Sense Circuit for a short to ground.
Perform POWERTRAIN VERIFICATION TEST VER - 6.
No ® Go To 6
6 If there are no possible causes remaining, view repair. All
Repair
Replace the Powertrain Control Module.
Perform POWERTRAIN VERIFICATION TEST VER - 6.
7 At this time, the conditions required to set the DTC are not present.
Note: Use the Freeze Frame Data to help you duplicate the conditions that
set the DTC. Pay particular attention to the DTC set conditions, such as,
VSS, MAP, ECT, and Load.
Note: Visually inspect the related wiring harness. Look for any chafed,
pierced, pinched, or partially broken wires.
Note: Visually inspect the related wire harness connectors. Look for broken,
bent, pushed out, or corroded terminals.
Note: Refer to any Technical Service Bulletins (TSB’s) that may apply.
Perform a wiggle test of the LDP wiring while the circuit is actuated with the
DRBIIIt. Listen for the LDP to quit actuating. Also watch for the Good Trip Counter
to change to 0.
Were any problems found?
All
Yes ® Repair wiring harness/connectors as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 6.
No ® Test Complete.

[Crystalion]

I have a 2000 Cherokee that just had this code pop up after.

A code for #6 misfire was original CEL and fixed. All the plugs were in pretty bad shape..My bad for not keeping up on her.
Plugs were changed and Jeep ran better than ever with stock Champions installed
Reset CEL and afer 2 days spprox 50 miles. the CEL light comes up again. With same one as above posted.
This is ONLY in the morning -now colder here in the NE.
Reset CEL and the Jeep is great all day and evening.
Next day after a short 4 hr night park CEL lights up again at 4 am start.
Reset again.

just now at 1am I went out and started it and NO CEL --------YET. I will be leaving for work at 4am as usual.



Thats alot of info about this code.
Has anyone else experienced this ??

Maybe Have found something ??


I'll keep posting about this since I didn't have this CEL until 1 day after plug change.

[Airjer_]

Chrysler products are more common for cracked evap hoses causing codes than anything else. With that said in the last month I have had three confirmed bad NLDP's, 2 bad gas caps, and 1 bad purge solenoid.

[Crystalion]

Originally Posted by Airjer_

Chrysler products are more common for cracked evap hoses causing codes than anything else. With that said in the last month I have had three confirmed bad NLDP's, 2 bad gas caps, and 1 bad purge solenoid.

Amazingly when I went to start her at 4am --Bam- friggin CEL again. Then fine ALL DAY AND TONIGHT after at least 20 starts .

I will check all the hoses since they could have been torn/Cracked when I moved aside the coil rail,

gonna use my other car today and see what happens when starting in some warmer daylight.

Thanks for your reply....

[fredjacksonsan]

CEL can be caused by a bad gas cap. How's yours? (I've always been accused of trying the simple fix first)

[wafrederick]

Only way to find an EVAP leak is with a smoke machine and it is not always a loose or bad gas cap.Chrysler is known for bad EVAP cannisters.

[Crystalion]

Originally Posted by fredjacksonsan

CEL can be caused by a bad gas cap. How's yours? (I've always been accused of trying the simple fix first)

Found a line attched to the exhaust manifold disconnected. The rubber boot was pretty fried up. So we will see .If its gonna happen it will be in 24-36hrs. Also DID check the gas cap about 10X. I also always give that one away to people with CELs on..LOL

[Airjer_]

Originally Posted by Crystalion

Found a line attched to the exhaust manifold disconnected.

I don't think so! There is nothing on your EVAP system that is attached the exhaust! There is nothing attached to the exhaust with a rubber boot either!?

[hundahunta]

maybe he meant the intale manifold. the vacuum elbow tends to distort and crack and fall off of the vacuum port on the intake

[Crystalion]

Originally Posted by hundahunta

maybe he meant the intale manifold. the vacuum elbow tends to distort and crack and fall off of the vacuum port on the intake

Well that could be it --the motor was hot when I looked at it and I worked about 70 hrs last week so maybe I had it wrong.

Either way if it stays off I will post the CORRECT place and name of the line.