Mechanic 12 Volt System Troubleshooting-Reverse Warning System Stuck On

Working on a fleet of buses has some amusing moments. Especially when 12 Volt systems and moisture come into play. Mechanics go to school to get the basics, then you need to use those basics and go much deeper. Experience indeed is the best teacher and mechanic information on symptoms and troubleshooting can be shared and recorded for the benefit of the entire shop and right here on this blog for future use.

Below is what I call a 'Mechanic's Special'

The driver complaint is the back up alarm and reverse lights come on all the time even in neutral. So the first thing to think about is what could possibly cause this to happen without touching the controls. With the key on we have full operation of the back up warning system. The HDX Thomas pusher we are working on has the VIM (vehicle interface module) mounted above the steering axle (Lots of snow and ice). This is the first place to check since the interface module receives the reverse signal from the Trans ECU after the driver selects reverse.   CLICK ON PICTURE TO ENLARGE.

The VIM has relays and fuses (BELOW) to control the circuits on the chassis side of the bus including the high idle, neutral start and reverse warning. Luckily once we pulled off the lid to the VIM we heard a buzzing noise. This is not normal and is a mechanic troubleshooting red flag, you want to look for abnormal mechanical situations.

After opening the VIM up the problem was obvious. The corrosion was making a circuit from battery to the reverse warning system. Moisture, oxygen and 12 Volt electrical circuits love each other and create double trouble after uniting for a given period of time.

Here is my 'KEEP IT SIMPLE' drawing (BELOW) of the circuit in question. The operator chooses reverse, the transmission shifts and the reverse signal is fed to the Vehicle Interface Module to the reverse relay and 12 Volt power feeds the reverse alarm and lights.

Once you know how a circuit works it makes the problem solving much easier and common sense will prevail. This problem can happen anywhere so be prepared. Checking electrical problem circuits and components closest to the environment pays off more times than not. I hope you got something out of this Mechanic Information.

Please leave a comment below and share any 12 volt electrical experiences you've had in the past or just let me know you got something out of this info.

Diesel Mechanic Books & The Importance Of Knowledge

Diesel Mechanic Books are the lifeblood for any Mechanic looking to increase his or her knowledge and efficiency. I have always depended on up to date information to reduce the guessing game when troubleshooting and repairing diesel engines. You will learn something new everyday and hopefully that new found knowledge will be in a positive light.

Knowing exactly how to disassemble and reassemble a diesel engine or adjust a fuel injection pump gives you the instant confidence you need to succeed. There is a difference between studying a book compared to a CD. Everyone has their preference. If you don't have access to a computer the book option is right for you.

BARRING OVER A CUMMINS ISC DIESEL ENGINE FOR A VALVE SETTING

Knowing torque specs & parameters along with a diagnostic procedure will save time and headaches. There are thousands of diesel engine books covering specific diesel engines and fuel injection systems that is an essential tool for the conscientious Mechanic who prides himself on the doing the job right. If you go into a job blind you're looking for trouble, the complexities of a modern diesel engine far exceeds the engines from 20 years ago. Emission Controls are computer driven and have to be respected using the right tools and know-how.

My First Diesel Engine Rebuild Story
When I was a greenhorn apprentice in my 2nd year I was instructed to rebuild a Cummins NTA 350 Diesel Engine (N = series T = Turbocharged A = Aftercooled). YIKES! Here I was 19 years old tearing down a truck driver's engine with his livelihood depending on me. This was my first rebuild so that Cummins overhaul manual went home with me every night. I studied that until I had it memorized. It would have been a losing proposition if I never had that diesel mechanic book by my side.

These engines were straight mechanical, the fuel injection timing was checked with 2 dial indicators. One on the injector cam lobe and the other on the piston. The timing was altered with shim / gaskets for the cam followers according to the dial indicator readings. The counterbore also had to be cut with a manual cutter where each cylinder wet sleeve fit into making sure there was the proper protrusion above the block surface to allow proper sealing for the head gasket.

I can't imagine what it would have been like to do this job without an engine manual. What an adventure that would have been!


ADJUSTING VALVES ON AN INTERNATIONAL DT466E DIESEL ENGINE

REPLACING A REAR SEAL ON A DT466E DIESEL ENGINE

In conclusion... having a reference to follow is essential when tackling a big job that you haven't performed yet or just need some torque specs. Most repairs on diesel engines are time consuming and could end up costing a bundle if one step is missed or a component isn't torqued down properly. It sounds easy pulling a head off an engine but each manufacturer has designed their diesel model differently with various procedures unlike any other engine on the market.

Each diesel engine running on the road today is unique with their stand-alone design and fuel injection system.  Diesel engine books will save your butt if you use them and follow the guidelines. Thousands of hours of research go into these books...it would only take a fraction of that time to look up a spec or procedure that could inevitably save your reputation. 

Please leave your comments, feedback & questions below.

Choosing A Mechanic Trade School Over College

Is A Trade School A Better Choice Over College?
Here's an interesting video on people enrolling into a trade school for a 10 month diesel engine training course instead of taking 4 years of college which comes with a much higher tuition. The enrollment fee is a fraction of what college costs and finding a job is faster and easier in the diesel engine mechanic trade.

Once you get your initial training at a trade school the chances of getting a job are much higher. Employers who want to hire a Mechanic for an apprenticeship like to find someone who has the basic training. Having a new kid on the block without any training means more supervision and less production.

Cummins ISB Troubleshooting Coolant In The Lubricating Oil

The Cummins ISB diesel engine is one of my favorites in the fleet, simply because it's easy to work on and really does not cause a lot of problems in the long run. Every Mechanic knows that easy accessibility is key to a smooth repair and these models are great to work on even if the back 2 cylinders are under the firewall on a school bus.

However no diesel is perfect so follow me through this quick troubleshooting procedure if you experience coolant in the lubricating oil.

1. The first thing to check is the lubricating oil cooler. The engine oil is cooled by way of the coolant running through a sealed core inside the housing. If it develops a leak you're stuck with coolant getting in the oil. The coolant core can be tested and replaced.

2. The next possibility is the air compressor cylinder head is cracked, has a defective casting (porous) or the head gasket is defective. This is an overlooked cause, the cooling system from the engine is connected to the compressor running through the compressor cyl. head.

3. If  your cummins isb engine came with an aftercooler it can be pressure tested to see if there is any problems with the inner core leaking.

4. The engine cylinder head is the next possibility with a leaking core or defective expansion plugs. The head must be checked out with a pressure test and magniflux test to find any leaks or cracks.

5. Last but not least is the worst case scenario, the cylinder block. If it's cracked or porous you may  be looking for a replacement block or reman (remanufactured) engine.

These are mechanic tips that you can use to get you started finding the cause of coolant in your engine oil.

CHECK OUT ALL MY PREVIOUS POSTS ON THE CUMMINS ISB ENGINE

Allison Transmission Codes & How To Retrieve Them

If you have ever wondered about Allison transmission codes and what they mean or how to retrieve them....look no further. Read the explanation below and leave a comment here on this post and I will reply with the code details. This is the first procedure a Mechanic carries out when there is a transmission complaint.

How To Retrieve an Allison Transmission Code

With the key on run... press the 2 arrows on your shift pad. You will get a D1 then 4 digits after that. The 4 digit number is the code you're after. To check for more codes press "mode" and D2 will show up with the second code (4 digits). Press Mode again D3 will come up with the fourth code and so on.

For Example: A Speed Sensor code is 2214 2212 or 2223. There are various checks you can perform. If you have a code let me know and I will post detailed transmission code troubleshooting information to help you out.

Allison transmissions come in different series, the 1000, 2000 and 3000 series depending on the size of your vehicle. The electronics is labeled as WTEC 1, 2, 3 and now 4. These are generations of the electronic systems built through the years. WTEC 3 is very common for older trucks, the tell tale sign of this type of system is the 3 plug-ins at the Transmission ECU.

This is a quick overview of Allison Transmission Codes and will be followed with a video demonstration on how to retrieve codes. Newer WTEC 4 systems require software called Allison Doc using a laptop. The video will be focusing on a WTEC 3 system using the shift pad to get codes. If you're a Mechanic, owner operator or truck enthusiast this procedure is the first step to take if you run into problems.

Check out all my Allison Automatic Transmission posts HERE  Full of Troubleshooting and Repair advice. Many faults can be repaired by running a new coaxial wire from the sensor to the ECU. If there is any interference or resistance issues with a signal to the ECU you will end up with a code.

UPDATE - VIDEOS  DEMONSTRATING HOW TO RETRIEVE AND CLEAR ALLISON TRANSMISSION CODES USING THE SHIFT PAD.

Here are 3 quick videos I made on how to use the trans shift pad to find codes. I set up a code by disconnecting the output speed sensor at the transmission. This will demonstrate what happens when a fault code occurs and what you can do to find out which code it is and how to clear it.

Video 1 - I'm purposely setting a fault code by unplugging the output speed sensor at the transmission.



Video 2 - Retrieving the transmission fault code using the shift pad.



Video 3 - Hooking the speed sensor back up to simulate the repair being completed and clearing the code using the shift pad.



As you can see Allison transmission codes are easy to read and clear using the shift pad. At the very least you can find out what the fault is and relay that information to your mechanic or use it to troubleshoot the problem yourself. I had a service call once in the middle of the winter, the bus was stuck in 1st gear.

Sound familiar? What had happened was the connector and harness accumulated so much ice around it the weight actually pulled the connector out of the output speed sensor socket. That was weird but made for a happy ending. Another common code is '3500' which is the battery voltage feed to the ECU, battery voltage is hard wired to the ECU so if their is any interruption you're going to get that code number.

Please post your comments and questions below and I will get back to you. thanks!

CLICK HERE FOR THE ALLISON SHIFT SELECTOR OPERATION AND CODE MANUAL.
NOTE: This is for a 2009 4th generation Allison Transmission.

Winterize Car Tips for Newbies

If you haven't had any experience working on your vehicle now is the time to learn some very basic winterize car tips that will save you from unexpected breakdowns & keep some money in your wallet. I found a great video presented by an instructor from Metro-Tech that goes through all the checks you need to know to help you and your vehicle survive the winter.

If you don't want to go through these steps yourself, at least you will know what has to be looked at the next time you go to your repair shop. You could realistically save an hour worth of labor at a shop and you will get into the routine of carrying out these checks every year. Buying your own fluids, parts and simple tools like a tire guage and coolant tester will save you from paying higher retail & shop labor costs.

While your on the road you might be stuck in a situation where you need to check your tire pressure or know what to check when you lift the hood on your vehicle. Watch these winterize car instructions before you head out on your next road trip.

Chevy 350 CID Engine - Tool For Priming Lubrication System

Below is our current job of the week, a Chevy 350 CID Gasoline Engine that needed new head gaskets. The heads had to be surface machined and valves reground. After reassembling the heads it's always a good idea to prelube the engine since it may take a little longer for the oil to reach the top end (valve train). You could prelube with grease like Lubriplate engine assembly grease but for the time it takes to prelube with engine oil it seems logical to do it the natural way to get the oil galleries full of clean oil.

The drive tool fits on top of the distributor drive (distributor removed). With a cordless drill it takes 10 to 20 seconds to charge up the lube system and the engine is ready to be fired up. You'll be amazed how fast the oil pressure climbs.

The tool below was fabricated by one of our shop mechanics who knows the importance of fast engine oil pressure build up after a major repair. once the engine cranks over the hydraulic theory kicks in. The pump being a positive flow gear pump will push the oil though the system in no time.

Cummins ISB Engine

For emission requirements the Cummins ISB engine was re-engineered to a 24 valve system. the acronym ISB stands for Interact System B with a Bosch VP44 rotary injection pump which was used until 2003. After 2003 it had an upgrade to a Bosch common rail high pressure injection system.

Torque was increased to 610 lb ft giving it higher low speed torque and a increased performance output compared to a V8 diesel in the medium duty truck industry.

5.9L Cummins ISB Engine Specifications:

The displacement is 5.9 Liters (359 cu. in.) with an inline 6 design. The firing order is 1-5-3-6-2-4 with a compression ratio of 16.3:1 and a high output version ratio of 17.2:1. Direct Injection started in 1998 which changed to common rail injection in 2003. The torque is 460 - 610 lb-ft @ 1,600 RPM with Horsepower rated at 235 - 325 HP @ 2,900 RPM.

From a Mechanic standpoint I really like the Cummins ISB engine and as you can hear from the video it really purrs nicely (After the compressor kicks out). The biggest problem we've had with the 2009 models is a minor exhaust manifold leak on a few of them and one compressor failure. In a fleet of buses that is an excellent record.

Online Car Repair Manuals - What Are The Advantages?

For the "do it yourselfer" or DIY Mechanic it's important to have the repair information handy before you start. There's no sense tackling a job if you don't know anything about it beforehand. The advantage of an online car repair manual is you don't have to buy hardcover versions, if you have a computer with a connection to the Internet there is virtually no holds barred with what you can do to save money repairing  your own vehicle.

There is no secret where to get information online. You can go to the many automotive forums and ask questions or post your repair knowledge. I personally want the information immediately if I have a job to do that can't wait. Online car repair manuals are subscriptions that are surprisingly inexpensive when you consider the amount of detailed info they provide. You can access technical service bulletins, recalls, torque specs, component diagrams, maintenance details and electrical diagrams giving you all the same advantages of owning a Chilton or Haynes hardcover version.

All you need to do is log in with a user and password accessing all the repair information you need to get the job done. Your only limited by the amount of tools and specialty tools you own. I have always referred to a manual because of the importance of torquing down components properly and knowing the step by step procedures before beginning any given repair job. I highly recommend an online auto repair manual to save you time, money and a little bit of frustration as well.

Troubleshooting Tips

Allison 3060 Automatic Transmission Fault Codes

 Here are fault codes that a reader left on a comment wanting to know what they were. The Allison 3060 Automatic Transmission is all electronic with sensors, solenoids a wiring harness and the Transmission ECU (electronic control unit).

The codes can be retrieved by pushing the 2 arrows at the same time (key on) to retrieve the 4 digit fault codes. Another method is to use the Pro Link Hand Held Reader. To clear the codes after you've repaired the problem hold the mode button until you hear 2 beeps. This has to be done during code retrieving.

Code 2511 means the output speed sensor has a zero speed reading. Check the speed sensor and connection, the ohm reading should around 300 ohms. Also check the ECU connectors. Make sure they are tight,clean and undamaged. Check the fluid level and check wiring to the sensor has no opens, shorts between wires or shorts to ground.

Code 2522 is related to 2511.... 22 being a sub-code.

Code 2312 is the shift selector. Check ECU for connectors, shift selector connector, check selector for proper operation and check the wiring harness for opens, shorts between wires and shorts to ground.

We have had lots of wiring issues and repaired a lot of these problems by running a new coaxial wire from the sensor to the ECU. There seems to be some resistance in the wire that causes improper signals to be relayed to the ECU.

Another area there has been faults is the shift selector pad. You can get a kit for the selector which isn't hard to replace.

If it's hard to push the selector to get into gear that's the first sign of trouble and a new selector pad would fix the problem. Here are all the posts I have produced on the Allison 3060 transmission with troubleshooting and repairs included. Scroll down and you will see some more Mechanic Information on the output sensor circuit.
Got Questions ? Please a comment..