Jeep Grand Cherokee 4.0L 2002 misfire initially when cold for a short time until warm. After mechanics tried to find problem, no. 3 & 4 plugs no spark. Two months later at the Jeep garage they replaced the ECM but 3 & 4 plugs still no spark. They said the ECM had blown. Coil pack was also replaced but no solution. Can the car start with ECM faulty or blown? What could be the cause of the minor misfire and no spark on 3 & 4 plug.

SOURCE: 2002 Jeep Grand Cherokee Lardo misfiring

You say you changed the cam sensor. A1391 code is a crank sensor on the top of the trans. bell housing.

SOURCE: MISFIRE CYLINDER #3 CHECK ENGINE LIGHT COMES ON VEHICLE

Check spark plug wires for corrosion

SOURCE: Changing spark plug wires on 2001 Jeep Grand cherokee

yah direct ignition coil pack does away for the need a a distributer cap and rotor.much higher energy ignition system where the computer tell when to fire.if that helps.not hard to change.as long as you change them one at a time so you don't screw up the order.

SOURCE: Ok I have 2002 Jeep Grand Cherokee, I have

The code indicates the coil pack or spark plug is malfunctioning. You can test this using an additional person. by removing the coil pack and spark plug, place the spark plug into the coil pack and ground the tang on the spark plug to the engine. Have someone start the engine and watch for a blue spark. if there is no spark, then the coil pack is malfunctioning. There is also ways to check the coil packs using a multimeter.

also, bee sure you didnt crack the ceramic part of the plug during initial installation.

Colin Stickland

• 22516 Answers
• Posted on Oct 03, 2010

SOURCE: i want a circuit diagram

you want what?? done you realise this is top secret information and its locked away and copyrighted ,even if you could get a diagram then a europeon market vehicle uses encrypted software so how could you trace a fault without knowing the encryption format .Just do what the reat of us do ,scrapyard -then ecu plus transponder plus chip from the key .