Today’s vehicle is a 1998 Buick LeSabre. The customer had taken it to another shop for a Service Engine Soon light and a hesitation on acceleration. The SES lamp was not on when she took into the shop. They couldn’t pull any codes and told her they couldn’t diagnose her car without codes, after having it for 2 days. They charged her 120.00 dollars and told her if the light comes back on, they would look at it again.
Needless to say, she was very unhappy and wasn’t willing to play games with them, that’s when she called me. I assured her I would be able to diagnose her car with no codes, as long as I could verify her complaint. She gave me the chance to look at it. I took it out for a road test and noticed it was misfiring under load and backfiring through the intake.
These are the misfires that were captured during the road test with the GM Factory Tech 2 scan tool, under heavy load.It was necessary to hook up my GM Factory Tech 2 scan tool and re-road test it. I found a steady misfire from cylinder #6 and some random misfires from cylinder #3. I came back to the shop and started a diagnostic strategy based on my findings. This lead me to inspect the ignition system and it’s related components. I was shocked that the other shop was unable to help this customer with her car. They should have at least tried.
This car has a DIS ignition system. It’s a waste spark design. Cylinders 1-4 share a common coil, as do 6-3 and 5-2. It has 3 coil packs and 1 control module. The spark plug wires looked fairly new and the # 6-3 coil had recently been replaced. The customer said that she had work done last summer in 2012. When I did my diagnostic inspection, I found the coil towers for cylinders # 1-4 and 6-3 were heavily corroded. The spark plug wires were also corroded and the wrong spark plugs were installed. The corrosion problem has damaged the plug wires and both the # 1-4 and new 6-3 coils. Whoever did the work last year failed to use dielectric grease on the plug boots. Moisture accumulated unchecked under the plug boots and corroded the towers and plug wires until it caused high resistance between the coil towers and plugs wires. They could no longer conduct the high KV required to operate the spark plugs during heavy demands on acceleration.
The corrosion on the coil towers.This was a simple no code diagnostic problem and was created by poor workmanship.
If the previous work would have been done right the first time, this would not be a costly and troublesome issue now. The lack of workmanship caused more damage than it fixed. Fix it right the first time and save money. Letting an unskilled person work on your car will cost you double and your vehicles reliability will be lost. Don’t be a victim of unskilled labor.
Today a customer had called me about his ’07 Malibu. He had the car to the dealer for a no crank, no start problem. The dealer told him that the BCM was the problem, so he authorized the repair for $800.00 dollars. The dealer installed the BCM and called him back to explain that the BCM did not fix the problem. They told him that they wanted to replace the power steering control module because they couldn’t communicate with it and that it would be the the next step for them to repair the car. They wanted to charge another $800.00 dollars to replace the unit, but they couldn’t guarantee it would fix the problem. The customer said not to do anything else to the vehicle and he then had it towed back to his home.
This is when he called me to ask if I could diagnose his car without replacing the power steering control module. I told him that I could find out what the problem is, without replacing anything. He approved my diagnostic time and I came to his home to find out what was wrong. After some preliminary diagnostics, I found no communication with the ABS, the EPS, the Radio, and the PCM control modules. After checking all the fuses and finding 1 of the PCM power fuses missing,I still had no communication with the Tech2 scan tool or between the other modules.
The system stored the common loss of communication DTC’s. B1001, U2100, D1001, U2000, U2127, U2100, U2103 and some BCM, DTC’s as well. Looks like the dealer didn’t finish with their work when setting up the BCM. I started my pinpoint tests and found a voltage drop of 7.2 volts to the PCM. The voltage drop was found at all the other modules that have no communication. I found 4 fuses in the UBEC that show the same voltage drop.
The customer isn’t ready financially to continue to fix the car at this time, due to the amount of money wasted at the dealer. He asked me if I could come back at a later date to finish the job when his bank account recovers from replacing the BCM that wasn’t needed. I told him I could and probably would be able to fix the car without replacing any other modules.The voltage drop is the cause of all his communication problems. It needs to be repaired to restore the proper voltage for the control modules to function.
I was called into a local shop for this one. Another shop replaced the motor for high mileage as the customer requested. When the vehicle wouldn’t start after the work had been done, they started to replace parts. A new crank sensor was installed. Then cam sensors were replaced. After trying the parts route they sent it to another shop. That shop couldn’t find the problem and called me in to check the PATS system. After checking the PATS function and finding nothing wrong, I suggested we check the crankshaft to camshaft correlation. The shop declined my advise. They called me back to program a replacement PCM. I did as they asked and after the programming was completed, the vehicle still would not start and had no codes stored. I suggested without knowing the base operating conditions, we could throw parts at it forever and never fix it. They authorized the time to do the CKP/CMP correlation verification.
I found the valve timing off by 15°. The engine builders improperly installed the cam chain by 15° advanced on the crank gear. Both cams are in sync with each other, but they missed the crank timing. This truck has been down for a month and the customer is upset to say the least. Now they are forced to remove the front timing covers and reinstall the cam chains to the proper specs. This will cause another week of wasted time and the customer is paying for his own rental car.
This LAB Scope image shows the 15° advance of the timing chains. The image below it shows the cams for bank 1 and bank 2 are in sync. This can only be done with a LAB Scope. Replacing parts without knowing what the real problem is, is a waste of time and money.
This one came to me from another shop. They wanted me to replace and program the PCM for a misfire problem. They’ve had this one to the dealer and still didn’t get the problem fixed. They replaced the ignition coil twice. They replaced all the spark plugs and wires. All 4 injectors and the MAP sensor. The customer has been driving it like this for 8 months. After performing the basic diagnostic inspection, I informed them a PCM replacement wouldn’t fix the problem. They let me run some advanced diagnostics with my Pico Scope. It only took about an hour to find the problem. Even the dealer couldn’t find and fix this one. Here’s a capture of the problem found with the Pico.
The top image shows ignition coil amperage issue’s on the #2-3 coil. Look at the peak amperage for the 1-4 and 2-3 coils and you’ll see the fault. I found the wires crossed in a connector that was replaced. I don’t know who did the work, but after correcting the wiring problem the vehicle ran great and the MIL lamp never came back on. A PCM for this car costs $700.00 dollars plus programming. It’s not a returnable part. It would have been almost $1000.00 dollars wasted. Here’s a capture after the repair. This customer was extremely happy to have her car back and running better than ever. Bottom image shows the proper coil amperage after the repair was made. A simple wire repair was the only problem and this customer has spent over $2600.00 dollars trying to fix it with no results.
Today’s fun project is a 2001 Chevy Silverado 1500 pickup with a 4.8L V-8
The customer’s concern was hard starting. It would start but had an extended crank time. It would eventually start after the 3rd or 4th attempt. The symptom was more pronounced after sitting for extended periods of a few hours or more. Here are some diagnostic Oscilloscope captures taken during the fuel system testing procedure. You can see how the fuel pressure is somewhat low with the engine running.
The fuel pressure regulator functions okay and the pump’s RPM’s are within normal operating range for a 10 segment pump. The current (amperage) load is also within specs. Notice how the fuel pressure drops off to zero within 10 seconds after the engine is shut down.
This is an abnormal pressure drop. This is the cause of the customer’s concern. A normal pressure drop should be less than 5 PSI after 15 minutes. The running fuel pressure should also be closer to 55 PSI. Cutting the old pump open for a visual inspection reveals the commutator bars looked okay. The pump’s internal fuel return check valve had failed allowing this abnormal pressure drop after pump shutdown. The initial pump prime of 2 seconds at key on couldn’t produce a high enough pressure to start the engine. After a 3rd or 4th key cycle the pump prime pressure increase was enough to start the engine. Always verify the cause of failure before replacing parts. Also verify proper operation after all parts replacements. The fuel filter was also replaced with the fuel pump to protect it from possible filter restriction damage.
To ZOOM for a larger image, just click on them.
This is the fuel pump’s armature with 10 commutator segments.
This is the current ramp (amperage draw) and segment signature of the pump while it’s operating.
This capture shows fuel pressure from key on engine off, to start up and engine running along with a fuel pump input voltage monitored channel at the pump and the relay output channel at the fuse block. This also checks for possible voltage drops in the fuel pump feed circuit. Voltage drops can cause low pump output problems that could lead to incorrectly diagnosed fuel pump replacement.
This capture shows the fuel pressure drop at shutdown. There is no substitute for a dynamic system test. This information is invaluable for proper fault verification to facilitate proper vehicle repair. No guesswork as to what’s wrong here.
The customer said it was over-filled with oil and leaks when running. I used my Smoke Wizard smoke machine to diagnose the leak and found it at the front crankshaft seal area. I advised the customer to replace the seal and the timing belt. After removing the front end and the balancer, I found the oil seal pushed out of the front cover. The excessively high oil pressure forced it out. I replaced the belt and the seal. What an oily mess!
2003 Cadillac DeVille DHS IPC Cluster
This is a 2003 Cadillac DeVille-DHS. The customer said that the tach and speedo had stopped working while driving. After some diagnostics and research, I found that the ignition 1 fuse had blown. Time to find the shorting circuit. It was necessary to isolate 7 circuit feeds from the ignition 1 fuse. The fault was intermittent and it took some time to isolate the 7 feeds down to the shorting circuit. Circuit isolation is the only way to pinpoint this type of fault when a single fuse feeds power to multiple components within the system. After narrowing it down to the rear integration module (RIM) and the rear object sensor control module (ROSCM) circuits, I was able to find that the harness rubbed through in the right rear sail panel pinch weld area and was shorting the power feed wire to the rear object sensor control module. The scan tool had communication with the module until the fuse would blow. 4 modules would stop communicating. The MIL lamp would also shut off. This looked like a PCM fault at first glance and very well could have lead to false PCM replacement, if not for diagnostic due diligence.
This one was a true automotive bug hunt.
Today’s fun job is an Audi A4 driver’s window problem. The customer’s concern is that the driver’s power window binds and stops working. Removal of the driver’s door panel revealed a faulty window regulator. This one is a big job and requires complete door frame and window removal to get the regulator out. Due to the extent of labor costs and the complexity of this job, I advised the customer to only use a factory replacement power window regulator. This assures a quality repair with a nationwide, Audi factory 12-month/12K-mile warranty.
This is the added benefit of buying a factory (OEM) replacement part.
Audi A4 Driver’s Door
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