Scorpio is unable to accelerate. Teana's acceleration engine whined.

Fault phenomenon A 2007 Teana car, equipped with VQ23 engine, has a mileage of 86,000 km. This car is an accident car. When the installation starts, the engine fault light is on and the acceleration is weak.

Fault diagnosis and elimination

After testing, the fault code is the power supply of the throttle and the function of the throttle. After each fault code is eliminated, the fault light will light up as soon as it is started, and it is the same fault.

First, check the insurance. After inspection, the insurance in the cab and engine compartment was not burned. Because this car was an accident car, it was replaced with a new IPDM, and the box was also equipped with a throttle relay, so it was replaced with another IPDM of Teana 2.0, but the fault remained. The voltage at the throttle was also measured. Two wires are 5V, and the rest are dead, just like the normal car, but the resistance of the accelerator motor is15Ω, while the other car is 35Ω. At this time, I thought that the accelerator had landed when the accident car was installed. I suspected that there was something wrong with the accelerator, but it still wouldn't work after replacement.

The engine harness was also damaged in the accident, but it was found that only a few wires were broken after being disassembled, which should not be a problem.

At this time, the fault codes are carefully analyzed, and two fault codes about the throttle valve appear at the same time. I think we should eliminate the power failure first, because if the power supply of an actuator itself has problems, what conditions are there to talk about the function of this electrical appliance? Therefore, the author decided to continue to start with insurance. This time, it was found that the THROTTLEMTR fuse of IPDM was not burnt out, as shown in figure 1, but there was no electricity at both ends of the fuse, which should be abnormal, but it was known by measuring the damaged IPDM. The fuse is powered by a thick black and yellow wire on a big plug. I feel that it should be powered by a big fuse, so I took a look at the big fuse at the battery and found that the third 80A fuse has been blown, as shown in Figure 2.

After replacing the big fuse at the positive electrode of the battery, the fault was completely solved!

Maintenance summary

Many reasons for failure may not be obvious, but often we think the problem is too complicated. When we encounter problems, we replace the accessories first, not analyze them. Generally, if we replace more than three parts, we will be confused and the problem will become more difficult.

Combined with this case, the author realized that he didn't work hard when he first checked the insurance, only knew how to measure the on-off of the insurance, and didn't know how to use the fault code for purposeful search, so he ignored the details that both ends of the throttle insurance were dead, which delayed the opportunity of troubleshooting!

The power supply for the throttle of this vehicle is from the positive battery through the 80A fuse on the positive battery to the 15A throttle MTR fuse of IPDM and then through the throttle MTR relay to the ECM, and then the ECM controls the throttle opening according to the working conditions of the engine. When the ECM detects the power failure of the throttle, the control of the throttle relay is turned off, so that the throttle enters the fail-safe mode, so the acceleration is weak.

Expert comment-Jiao Jiangang

After reading this case, I feel that the author's thinking is not very clear and he doesn't work according to the general rules of troubleshooting. The description of fault content is not very clear. If the fault code and its explanation are clearly introduced and the circuit diagram of the throttle system is attached, the effect may be better.

Because the author did not work according to the general rules of troubleshooting, the author's maintenance steps were clumsy in the maintenance process. The correct maintenance steps should be: first, according to the content of the fault code, determine the corresponding fault location; Then, according to the instructions in the repair book (or related materials), check the wiring, power supply and grounding of relevant sensors or actuators. If we follow this method, I think we should find the fault point soon.

Not only for the author of this paper, but also for the technicians working in the front line of auto repair, I hope that in the future work, I can establish a comprehensive and perfect maintenance idea and avoid hasty and random behavior, which is believed to be very beneficial to the work.