2004 Isuzu NPR

Engine Performance problem
2004 Isuzu NPR V8 Two Wheel Drive Automatic 65650 miles

VIN #4KLC4B1UZ4J801446 / 5.7l GAS ENGINE
Shut truck off on route; went to restart 30 min later, truck started but red check eng. Light on & truck would shift into gear but wouldn't move. Called wrecker; wrecker showed up one hour later & needed truck pulled up to load. Started truck and red check eng. Light still on but went in gear and was able to drive to wrecker. Towed to business; checked all fluid levels, OK. Started truck up, no engine light; was able to pull a P2135 code (TPS positive sensor / switch A/B voltage correlation). Checked TPS, nothing obvious & road tested truck for 30 min & restarted, good and no light coming on. Would appreciate any suggestions/diagnostic help and especially any schematics showing circuit checks including ohm checks; don't want to replace TPS sensor without know that's the problem, thanks.
April 26, 2009.

Turn ON the ignition, with the engine OFF.
Observe the throttle position (TP) sensor 1 and 2 Agree/Disagree parameter with a scan tool.
Does the scan tool TP sensor 1 and 2 Agree/Disagree parameter indicate Disagree?Disconnect the throttle body harness connector.
Connect the jumper wires between the TP sensor terminals of the throttle body harness connector and the corresponding TP sensor terminals of the throttle body.
Observe the TP sensor 1 and 2 with a scan tool.
Slowly open the throttle blade to wide open throttle (WOT) and back to the closed throttle position several times by hand.
Does the TP sensor Agree/Disagree parameter change from Agree to Disagree during the above test?If the TP 1 and 2 agree/disagree then replace the throttle body. Follow this info and post back with what you find.

Brian 1
Apr 28, 2009.
The first place to check when an NPR shows these signs is the main harness block. It is located behind the grill. A 10mm socket removes the one screw on the grill, and then just pull it from the clips holding it on. A 10mm removes the retaining screw for the harness block as well. Often this connection gets moisture and funk in there and messes up voltage correlations and what not. Clean it up with such as brake cleaner and compressed air.

Oct 13, 2014.