Memorable Asian vehicle fixes

Aug. 1, 2018
Don’t fear Asian vehicles! Since many companies already share parts and technology, you will notice that Asian vehicle are not that much different than domestic vehicles. Just like any other vehicle that comes into your shop with a problem, you need a game plan on how you’re going to address the problem.

Don’t fear Asian vehicles! Since many companies already share parts and technology, you will notice that Asian vehicle are not that much different than domestic vehicles. Just like any other vehicle that comes into your shop with a problem, you need a game plan on how you’re going to address the problem.

2010 Toyota 4Runner

Our first vehicle is a 2010 Toyota 4Runner 1GR-FE with 128k that came in with the ABS light illuminated and the owner complaint of a braking issue. We started our diagnosis with a Q&A of the owner, followed by a short test drive and a visual inspection before connecting our scan tool.

Figure 1

After we connected the Toyota TechStream scan tool (Figure 1) we found the following DTCs; C1404 (Open or Short in Rear Speed Sensor LH Circuit), C1408 (Open or Short in Rear Speed Sensor LH Circuit) and C1416 (Open in the Sensor Signal Circuit of a Malfunction area occur 255 times or more). Our next step was to take a look at the DTC supporting information - Freeze Frame. As you can see from the Freeze Frame data (Figure 2), the Left Rear wheel speed was recorded moving at 0 mph, while the other wheels were displaying 26 to 27 mph. 

Figure 2

The source of the DTC could be caused by the rear speed sensor, skid control sensor wire, speed sensor circuit, speed sensor rotor and/or the master cylinder solenoid skid control ECU. Common problems with theses sensors include debris, a sensor that has moved from its normal position and defective sensors. We took the vehicle for a test drive with the scan tool connected, making sure we drove it in a straight line at 28 mph to see if the DTC would reappear. The DTC returned right away so there was no need to drive the vehicle in reverse at two mph as recommended by Toyota. 

With the test drive confirming that the circuit had a problem, my lead technician (Bill) checked the wiring to make sure there were no connection problems. After the wiring checked out, the next step was to call the 4Runner owner and recommend that both rear wheel speed sensors be replaced. Take notice, that we did not use a labscope on this problem since Toyota service information had specific testing of the circuit that would confirm the problem without using any other tool besides the Toyota Techstream. Why take out the backhoe when a shovel will do the job? We need to remember that we sell our time to the customer, so we need to diagnosis the problem in the easiest and most efficient way. 

2005 Toyota Tacoma

A 2005 Toyota Tacoma with a 1GR-FE V6 4.0L came in with an overheating issue and the MIL on. This vehicle had 123,938 miles on the clock and has served our customer very well over the years. After we connected our scan tool, we discovered that the MIL was illuminated due to a misfire in number 6 cylinder. 

As Bill began his diagnostic game plan, he came upon a low coolant level as part of his preliminary checks. He also found that the scan data displayed a P0306 DTC that could be caused by a mechanical, ignition, or fuel issue. He proceeded to check all the easy stuff first,  performing a relative compression test, ignition and fuel system test. After performing a basic cooling system pressure test that failed to hold pressure, his next step was to check for a head gasket problem since this is a common issue on this Toyota V6 engine. Bill’s decision to proceed in this direction was based on the test results from the relative compression test that indicated normal results, while the cooling system pressure test failed. 

His next logical step was to check for CO2 in the cooling system using the ATS Bullseye CO2 tester. In our shop, we have had excellent results while using the BullsEye tester to uncover head gasket or cylinder head issues. On this vehicle, the test results indicated CO2 levels that could be the result of a cylinder head gasket, head or engine block problem. You may be thinking that we should have used the engine block tester that uses the liquid blue dye and changes color when there is a compression leak issue. Our experience with the block test has not always been good or accurate enough at detecting problems. 

Figure 3

While using the ATS Bullseye CO2 leak detector, we uncovered (Figure 3) a CO2 leak that was displayed by the tool’s led bar illuminating along with an audible alert. The confirmation provided by the Bullseye tester was what we needed to inform the vehicle owner that we would need extra diagnostic time. Our next step in the confirmation process was to perform a cylinder leak down test in order to complete the diagnosis of this engine. Notice, we did not perform a compression test since we already confirmed that the engine’s relative compression was within range, the cooling system had already failed the pressure test, and now the leak detector was indicating high CO2 levels in the coolant. 

Since this engine had an issue with overheating, we explained to the owner that we had to remove the cylinder heads and send them to the machine shop to be pressure tested. When we removed the cylinder heads, we noticed a difference in the head gasket near cylinder number 6. We checked the engine block with a straight edge and feeler gauge to make sure that it did not warp. Since it checked out, we just needed to wait to hear back from the machine shop. We received a call from the machine shop informing us that the heads were in good shape except for cylinder number 6. The valves in cylinder number 6 were not sealing properly most likely due to the head gasket failure that was causing coolant to leak into the cylinder.

Figure 4

This Toyota 4.0L V6 engine utilizes 3 timing chains and tensioners (Figure 4) along with VVT (Variable Valve Timing) only for the intake cams. There are two small chains that go from the exhaust gears, that are just a run of the mill plain gears that are connected to the intake VVT gear on each bank of the engine. The long, big chain goes from the crank pulley to the VVT intake gears to the center idler gear. One of the most important components is the Camshaft Timing Oil Control Valve, aka the solenoid that controls the oil flow to the camshaft phaser. We made sure that the solenoids screens were clear of debris and that the resistance and current readings were good before we reinstalled them. After we installed the reconditioned cylinder heads, new timing chains, tensioners, chain guides, thermostat, Toyota engine coolant/antifreeze, full synthetic Pennzoil oil and a NAPA oil filter, the engine was now ready to be started up. Once the engine started up it ran fine with no misfires or any signs of a coolant issues. The Tacoma was test driven to make sure there were no issues before we returned it to the owner.

2002 Lexus GS 430    

A 2002 Lexus Model GS 430 V8-4.3L with 184,733 miles on it came in with a complaint of a Check Engine light on and a loss of power. Our first step was to perform a visual inspection followed by connecting our scan tool. We checked Identifix to see if there were any common problems and found that there were a few issues with the Knock sensor. With our scan tool connected the data revealed a P0325 Knock sensor (left bank circuit problem) DTC. The next step was to check the circuit, so we disconnected the EC1 connector and followed the information described in ALLDATA. 

With a labscope connected to KNK1 and chassis ground we raised the rpms to the described amount and viewed the data. With the other channel connected, we were able to compare the left bank (the side throwing the code) to the right bank. What we noticed was the waveform voltage amplitude was different between the two. The left bank did not display the same voltage height or frequency as the right bank. We called the vehicle owner and provide him with the information about the job that we would need to perform to solve his problem. We suggested, since the engine had high mileage on it and the intake manifold was going to be removed, it would be a good idea to replace both Knock sensors along with the starter motor. The vehicle owner only gave us the approval on both knock sensors, so the old starter remained in the engine. With the two new sensors installed and the cooling system refilled and bled, the DTC was cleared and the car was test driven. The vehicle was now back to the proper operating condition and the Lexus owner was happy. 

2005 Toyota Camry

Our next vehicle was a 2005 Toyota Camry 3.0L V6 that came in with the Check Engine light on (Figure 5) and three DTCs. Since it’s a driveability issue, we figured we’d get the most information in the shortest amount of time using a good Global OBD II scan tool rather than connecting an enhanced scan tool. The EScan Pro allows us to check relative compression, MAF, fuel trim and catalyst efficiency as well as DTCs in a matter of minutes. 

Figure 5
Figure 6

The EScan provided us with a direct path in diagnosing our problem vehicle. The scan tool data (Figure 6) uncovered these DTCs; P0174 (Bank 2 System Lean) and P0430 (Catalyst System Efficiency Below Threshold Bank 2). There was a pending DTC P0420 (Catalyst System Efficiency Below Threshold Bank 1). Looking at the Freeze Frame data, we noticed that the LTFT (Long Term Fuel Trim) on Bank 2 was at 26 percent while Bank 1 was 22 percent. Take notice that the Freeze Frame was captured a 618 rpms and at 0 mph. The engine temperature was not fully warmed up since the temperature was only at 177 degrees F. The Freeze Frame for the P0430 was captured at 210 degrees F and the vehicle speed was 55 mph. The LTFT on Bank 2 was much lower at 3 percent while Bank 1 was only at 0.7 percent. What most likely was occurring was that the engine was being command to go rich at idle, dumping too much fuel and taking out the Bank 2 catalytic converter. 

Figure 7
Figure 8

As we graphed the Bank 1 and 2 rear O2 sensors (Figure 7), we noticed heavy frequency indicating that the efficiency of the converters was not normal. This led us to our next step to check the Fuel Trim chart (Figure 8) that you can see has a high fuel trim command at the lower end of the chart. This usually indicates that there is a lean condition only at idle since the number greatly reduces as the chart is filled up. Notice once we get past the 30 percent range of throttle the numbers go in to the normal range indicating that it’s not a fuel delivery problem due to a clogged fuel filter, voltage drop at the fuel pump or for that matter a bad fuel pump. The results also indicated that the fuel trim issue is not a load sensor issue since the fuel trim numbers do not rise throughout the full range of the chart. It’s a good idea to see if Fuel Trim goes down as we raise the rpms up. If the Fuel Trims do head south, it indicated that the problem is a vacuum leak issue. This Camry needed some work from an intake gasket, fuel system cleaning, spark plugs, air filter and most likely catalytic converters. The owner decided not to repair the vehicle but rather lease a new vehicle.

2007 Toyota Tundra 
Our final case study is on a 2007 Toyota Tundra that was towed in from another shop with the complaint of a no start condition. The shop stated that the vehicle just stopped running, so their customer had the vehicle towed to their shop. They confirmed the no start condition then connected their scan tool only to find that there was no scan tool communication with the Tundra. Their next step was to install a remanufactured PCM only to come up with the same results. 

They call us and asked if we could program the truck, thinking that would get the Toyota running. Once the Tundra arrived, Bill checked it out only to find that the PCM was not communicating with any of our scan tools. Bill called the shop and explained that he could not program the vehicle since there was no communication. He suggested we diagnosis the problem and asked for two hours of diagnostic time to check the vehicle out further. 

Figure 9
Figure 10

Bill started by installing a breakout box (also known as a “BOB”) at the DLC (Figure 9) then measuring the CAN line resistance using the ohm meter. As you can see from the picture (Figure 10) of the meter, the ohm resistance reading was 63.3 ohm - within specifications. Now it was time for Bill to leave the shovel behind and get the backhoe out. He now connected the EScope Elite to pins 6 and 14, CAN high and low. Remember “KISS” (Keep It Simple Stupid!), always start with the easiest test first, as Bill did by checking the resistance with the ohm meter before moving up to using a labscope.

Figure 11

  Take a look at the scope communication screen (Figure 11) and see if you can diagnosis the problem. It looks like both CAN high Pin 6 and low Pin 14 are producing a 1v voltage signal. The voltage of CAN high signal is going from 2.5 volts to 3.5 volts while CAN low was producing a signal that was 1.5 volts to 2.5 volts. Your first thought maybe that there is something on the vehicle pulling down the voltage signal. Well if that is what you think is causing our no communication / no start problem, you would be dead wrong. There is nothing wrong with the voltage levels, but rather with the frequency of the signal. The one volt level is normal so don’t expect a 5 or 12 volt CAN signal on this CAN system. 

The proper diagnosis and repair of this vehicle was attributed to the training that my lead tech recently attended. This past March 17th Bill attended our 15th annual TST Big Event where we had three good instructors, with two of them covering CAN. At the end of the first seminar that was taught by Snap-on’s Jim Mortiz, CAN was covered from the ground up. This was followed after lunch by the other CAN presentation by Automotive Test Solution’s (ATS) Bernie Thompson. If you ever had the experience of being in Bernie’s seminars you know you must buckle up. He started off like a rocket on a launching pad taking off into space. Bernie proceeded to explain the CAN system and following it up with real world problem vehicles he had diagnosed and repaired. Bill listened carefully to Bernie’s presentation and that provided him with the information he would need to repair this Tundra. 

Figure 12

Bill asked me to take a look at the scope screen capture that he had taken to confirm if there was a problem. I suggested that he locate the CAN disconnect if this vehicle had one and start removing components from the BUS. Unfortunately, this vehicle did not have a CAN disconnect comb that allows systems to be removed from the BUS. Bill proceeded to disconnect the component that we have seen to be biggest problem on other Toyota Tacoma’s. The problem component that was preventing the CAN system from properly delivering packets was caused by the AIR (air injection reaction system) that had a shorted solenoid. Once Bill disconnected (Figure 12) the air pump connector, the CAN packets returned to normal, now having a proper frequency that allowed the engine to start. The scope capture (Figure 13) of the CAN pins 6 and 14 as you can see now looked different that resulted in the engine starting. 

Figure 13

Knowing how to use a labscope is a very important step in diagnosing a CAN system issue. The labscope provides an inside picture in to the electrical system that it is connected to. It’s a good idea to get yourself a good labscope and know how to use it. As in this case study, we had the Escope Elite 4 along with the proper training on how to use a scope. In fact, the training that Bill had recently gone through was one of the biggest factors in resolving the CAN issue on this vehicle. Bill attributes his success in diagnosing and repairing this CAN problem vehicle to the seminar he attended taught by Bernie Thompson. Remember we need to attend seminars and hands on training classes to be updated so we don’t evaporate. 

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