Posted on November 15, 2011 - by Richard

2002 Dodge Caravan Emissions Problems

Symptoms for 2002 Dodge Caravan Emissions Problems

Do you have a fix for 2002 Dodge Caravan Emissions Problems? I got a call from an ATS member because his vehicle was using too much gas. The vehicle has been in 2 garages and they can’t seem to fix the problem.

In the last 3 months, the following were done: complete tune up like replace spark plugs, air and fuel filters and lately the ignition coil packs. They also flushed the injector system to make sure all injectors are clean. After all these jobs, the emission was still high because he was still using lot of gas.

In desperation, he got himself a good scanner and contacted ATS when he found he got a code P0172. Aside from this code, the fuel trim was -25 and the oxygen sensor reading was stuck or not fluctuating as normal. Doing a closer inspection, he did a compression test and all cylinders were ok.

However, he found out that cylinder 1&5 has fouled up spark plugs. After cleaning the plugs, he scanned again the injector wave pattern and found out the injector 1&5 looks like erratic compared with other cylinders. Are these injectors the cause of high emission?

Important Notes for 2002 Dodge Caravan Emissions Problems:

P0172-code means engine fuel system rich, full lean trim

Normal LTFT is between +- 10, -25 mean rich fuel mixture because of bad fuel system (injectors?)

Engine size for this is 3.3L with 1 injector per cylinder using ignition coil packs (no distributor)

Diagnostic for 2002 Dodge Caravan Emissions Problems

Looking at the information given here about the vehicle, it is clear that the culprit is coming from the 1&5 injectors and its circuit. The recommended way in checking this is to use a scanner so the injector wave pattern can be seen.

If the injector pattern deviates from other injectors, try this: look at the ecm wiring diagram for injectors 1&5 and check all the connections upto the ecm terminals. On closer analysis, the ecm driver for both 1&5 injectors is common for both injectors. To test the wirings, disconnect one of the injector plug in terminal and see if the other injector wave pattern changes. Do the same on the other injector.

Assuming both injectors will not show any change in wave pattern, does a resistance check between the injectors and ecm wiring harness. If resistance is lower than 5 ohms, then we know the injector harness is OK.

You can also measure the total resistance of each injectors 1&5 and they should be the same as per vehicle’s requirements (or call ATS). So if the harness is good and the injectors are good which were replaced by the last garage, it’s a safe bet the real problem lies in the ecm. A power and ground supply test will verify this.

Final fix for 2002 Dodge Caravan Emissions Problems

When the vehicle was tested using this ATS information, it was discovered that the ecm has an internal driver’s problem. A new rebuilt ecm fixed the problem.

More tips for 2002 Dodge Caravan Emissions Problems:

1.) The easiest way to check hard to find poor emission problems is to use a scanner with live stream data so you can see what the engine is doing internally. If you couple this with ATS wiring diagrams and instructions given by ATS, there is a good possibility that this difficult emission problems can be solved.

2.) Don’t forget your troubleshooting basics when testing engine integrity: vacuum intake and exhaust reading, fuel pressure test, cylinder compression test and making sure you scanned for codes. Getting a fault code will direct you to the specific engine circuit instead of wasting your time in time and parts that you don’t need.

Thanks,

Richard