Jeep 4.0L Index of Articles

How To Test TPS Codes: P0121, P0122, P0123 (1997-2001 Jeep 4.0L)

How To Test TPS Codes: P0121, P0122, P0123 (1997-2001 Jeep 4.0L)

In this tutorial I'm gonna' show you how to test the throttle position sensor (TPS) on your 4.0L Jeep Grand Cherokee (Cherokee, Wrangler) without a scan tool. This is a very accurate test of the TP sensor done with a multimeter... that will tell...   read more >>

Front Oxygen Sensor Heater Test -P0135 (1996-2000 Jeep 4.0L)

Front Oxygen Sensor Heater Test -P0135 (1996-2000 Jeep 4.0L)

A trouble code P0135: O2 Bank 1 Sensor 1 Heater Circuit Performance on your Jeep Cherokee (Grand Cherokee, Wrangler) lets you know that there's a problem with the heater element of the upstream O2 sensor. This code usually points to a bad...   read more >>

How To Test For A Blown Head Gasket (Jeep 4.0L)

How To Test For A Blown Head Gasket (Jeep 4.0L)

This article will present you with the four most common ways to test for a blown head gasket on a Jeep 4.0L inline 6 cylinder engine. All four are very simple and easy tests that will help you confirm (or disconfirm) a blown head gasket. Two...   read more >>

How To Test The MAP Sensor (1997-2003 Jeep 4.0L)

How To Test The MAP Sensor (1997-2003 Jeep 4.0L)

The fastest and the most accurate way to test the manifold absolute pressure (MAP) sensor on your 4.0L equipped Jeep Cherokee (Grand Cherokee, Wrangler) is to bench-test it with a multimeter. In this tutorial I'll show you how in a step-by-step...   read more >>

How To Test Engine Compression (Jeep 4.0L)

How To Test Engine Compression (Jeep 4.0L)

An engine compression test is fast becoming a key test in diagnosing a hard to troubleshoot misfire condition. In this article, you'll learn how to do the engine compression test and, more importantly, how to interpret the results of the test on...   read more >>

How To Test The Starter Motor (Jeep 4.0L)

How To Test The Starter Motor (Jeep 4.0L)

Testing the starter motor, to see if it's the cause of the No Crank Condition on your Jeep, is not that hard. As a matter-o'-fact, testing the starter motor, to see if it's good or bad, is something that you can do at home. In this tutorial I'll...   read more >>

How To Test The MAP Sensor (Jeep 4.0L)

How To Test The MAP Sensor (Jeep 4.0L)

The manifold absolute pressure (MAP) sensor on your 2.5L, 4.0L Jeep Grand Cherokee, or Wrangler, or Cherokee, can be tested with a multimeter and a vacuum pump. You don't need a scan tool! So if a diagnostic trouble code P0108 (OBD II equipped) or...   read more >>

Jeep PWM Fan Relay Test Troubleshooting An Overheating Condition

Jeep PWM Fan Relay Test Troubleshooting An Overheating Condition

This article will help you to diagnose the Pulse Width Modulated (PWM) fan relay on the 1999-2004 Jeep 4.0L Grand Cherokee SUVs and/or the codes P1491 (Radiator Fan Control Relay Circuit). The dealer, at the time of this writing, will charge you...   read more >>

How To Test The Oxygen Sensor (O2S11) Bank 1 Sensor 1 (Jeep 4.0L)

How To Test The Oxygen Sensor (O2S11) Bank 1 Sensor 1 (Jeep 4.0L)

The upstream oxygen sensor on your OBD II equipped Jeep 4.0L SUV can be tested, and in this article, I'll show you how in a step-by-step fashion. This article will help you to test the upstream oxygen sensor (commonly known as the O2 Sensor Bank...   read more >>

How To Troubleshoot A BAD Fuel Injector (Jeep 4.0L)

How To Troubleshoot A BAD Fuel Injector (Jeep 4.0L)

Fuel injectors rarely go BAD, but when they do, they will cause the engine in your Jeep 4.0L Grand Cherokee (or Cherokee or Wrangler) to miss and/or idle rough. The really cool thing is that they can be easily tested with a multimeter and this...   read more >>