Tip & How-To about BMW 325

General diagnostics

When you get fault codes they are the worst, but here are a few tips on doing your own diagnostics at home. The equipment that you will need is pretty basic and do not generally cost much and you can make a few yourself. I like to have at least 3 jumper wires, a test light, and a digital multimeter.

This is a basic model and can go for anywhere from $15-$30 USD
Test Light:
This is the best way for checking continuity on just about any motor or sensor.
Jumper Wires:
These are just about essential for transferring power over a suspicious relay or fuse.

A lot of the times users ask us on our website about the best way to check if a relay is bad or if a component is faulty. With a jumper wire and a test light at your side they can ultimately find your trouble.

How to use a Test Light;
Test lights are useful, but they can be harmful too, that's why knowing what and how to do with then is important. test lights generally just jump a power source and illuminate a bulb. this is useful, however you can also short a circuit with one or send too much voltage to a resistor (sensor) also. that is why using a test light to check continuity of a 12v circuit is basically all you can do with it, but that is more then enough in most cases.
When using a test light connect the clamp to a good known ground and touch the probe to the component that is suspected of being shorted to ground. if the light comes on then you know that the component is grounded. Therefore you have continuity. No light no power. you can also test for typical short by clamping the test light to the battery positive and testing grounds.

How to use a multimeter;
The multimeter has been around for about 40 or so years and since electronic fuel injection had become the modern technicians "go to" tool for all kinds of check engine and short circuit issues.The models vary from manufacturer to manufacturer, but al do the same thing and that is tell you whether or not there is the right resistance and good voltages coming into and out of sensors, motors, and batteries.

How to use Jumper Wires;
Jumper wires are easy to make and even simpler to utilize. they basically are used to test whether or not relays, fuse links, and circuits for bad lines receiving power or whether or not there is power going to the component in question.

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1 Answer

why is it in limp mode and what can I do to fix it?

Limp home mode is triggered when the management ECU recognises a fault. The fault is not usually obvious and diagnosis usually starts with a code read and probably an examination of live data with a scan tool.
The faulty item should then be removed and tested and repaired or replaced and then the recorded fault code cleared and the live data rechecked to verify a good repair.

Often even after a repair has been completed limp mode will continue until the code has been cleared with diagnostic equipment.

Aug 08, 2015 | 2004 Chrysler Sebring

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how can i reset a check engine light without taking the jeep to a shop. the code was for a emmissions problem i changed all the hoses that were cracked, now i just want to stop the check engine light to see if the problem is fixed. thanks

Your system goes through self-diagnostics every fifty miles or so. If you just drive it, once the system sees no faults the light should go off. You can also clear codes using a scan tool.

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Engine Fan Stays on

Hi Neil,
The best way forward is to get the fault codes read using the on-board diagnostic system. You can either get this done at a suitably equipped garage or do it yourself with free VAG diagnostic software, a £15 interface cable and the use of a laptop computer. This should indicate where the fault lies. If a sensor is throwing a fault code, it could still be just a dirty electrical connector on the end of the cable, and not the sensor itself.
Once you have the list of fault codes, get them cleared, run the car for a few miles and check the codes again in case some of them were old ones that no longer apply.
If you get back to me with the list I will try to help you further.
Cheers, D.

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