Exception in rendering!

Message: window is not defined

ReferenceError: window is not defined
    at new c (/tmp/execjs20161208-55793-1mk8be1js:136:3912)
    at m.mountComponent (/tmp/execjs20161208-55793-1mk8be1js:47:15602)
    at /tmp/execjs20161208-55793-1mk8be1js:49:31860
    at a.r.perform (/tmp/execjs20161208-55793-1mk8be1js:47:12503)
    at Object.a [as renderToString] (/tmp/execjs20161208-55793-1mk8be1js:49:31821)
    at r (/tmp/execjs20161208-55793-1mk8be1js:50:21164)
    at Object.S.ReactOnRails.serverRenderReactComponent (/tmp/execjs20161208-55793-1mk8be1js:32:6073)
    at eval (eval at <anonymous> (/tmp/execjs20161208-55793-1mk8be1js:173:8), <anonymous>:10:23)
    at eval (eval at <anonymous> (/tmp/execjs20161208-55793-1mk8be1js:173:8), <anonymous>:17:3)
    at /tmp/execjs20161208-55793-1mk8be1js:173:8

P0804 OBD-II Trouble Code: Upshift (Skip Shift) Lamp Control Circuit Malfunction

='https://d3vl3jxeh4ou3u.cloudfront.net/Diagnostic%20Check%20Engine%20Light%20with%20logo.jpg' class ='qna-article__image' alt='Check Engine Light'/>

What the P0804 code means

Your vehicle’s powertrain control module (PCM) has detected a malfunction in the one through four skip shift solenoid lamp control circuit. The one through four skip shift solenoid control circuit is also known as the upshift control circuit because it prevents you from shifting through second and third gears. This is to improve fuel efficiency by eliminating the higher RPM levels that come with shifting through lower gears. The P0804 code lets the driver know that the one through four skip shift system has been turned on. Please note that this pertains only to vehicles with manual transmissions. If you have an automatic transmission and this code appears, you should suspect that you have a defective PCM or that there has been a programming error.

What causes the P0804 code?

If your PCM recognizes an abnormal voltage or resistance reading from the skip shift lamp control circuit, the P0804 code will be stored and you will see that a Check Engine or Service light will come on to let you know that something has malfunctioned. But beware that on some vehicles a lamp will not illuminate to let you know something is wrong. In these cases, you will have to trust your vehicle’s symptoms.

According to most technicians, the most common causes of the P0804 code are a defective skip shift indicator lamp bulb, skip shift solenoid, skip shift relay, fuse, or actuator. Some other causes could be open, shorted, or corroded wiring or electrical connectors. If you have installed an aftermarket skip shift, then you may also see the P0804 code appear.

What are the symptoms of the P0804 code?

Some symptoms of the P0804 code include a skip shift indicator lamp that is not coming on, a lit Service Engine Soon lamp, and a stored code.

How does a mechanic diagnose the P0804 code?

You will need a scanner (or code reader) and a digital volt/ohmmeter to diagnose this problem. The skip shift solenoid is usually found mounted in the transmission housing near the shifter assembly. Begin with a careful visual inspection of all wiring and connectors. Make sure to repair or replace any disconnected, damaged, shorted, or corroded connectors, wiring, and other components. After the codes are cleared, start the vehicle and see if the code reappears. If the code appears immediately, using the digital volt/ohmmeter check your battery voltage on the input side of the one through four skip shift solenoid. If there is no voltage on the input side of the solenoid, disconnect any related control modules and test for continuity between the system relays and fuses along with the input circuit at the one through four skip shift solenoid. If voltage is present on the input side of the one through four skip shift solenoid, use the scanner to command the solenoid “ON” and test for voltage on the output side. If you see voltage on the input side but nothing is happening on the output side, you might have a faulty or misadjusted one through four skip shift solenoid.

Common mistakes when diagnosing the P0804 code

A large problem with the P0804 code is that your Service Engine Soon lamp might not come on, making it difficult to know that a malfunction has occurred.

How serious is a P0804

Although a P0804 is not as serious as some other codes, your vehicle should still be examined as soon as you notice the malfunction. If ignored for too long, this issue could damage other components in your vehicle.

What repairs can fix the P0804 code?

You may need to replace or adjust your solenoid and then retest the system afterward to ensure a successful repair. If there is voltage present on the output circuit of the one through four skip shift solenoid, you should check your circuit continuity and resistance between the switch and the PCM. In extreme cases, you will have a defective PCM, but this is rare.

Additional comments for consideration regarding the P0804 code

Like many trouble codes, a P0804 can become complicated if you do not have the proper diagnostic equipment. Therefore, if you are doing this yourself, it is important to do the proper amount of research before you begin to work. Also, do not hesitate to contact a professional technician to ask questions about the best way to solve your issue. It is always better to consult an expert when you are unsure of what you are doing.

Need help with a P0804 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

Post a question and get free advice from our certified mechanics.

ASK A QUESTION

More related articles

How to Renew Your Car Registration in Oklahoma(DELETED)
Having your car registered with the Oklahoma Tax Commission is an important part of driving legally in this state. You will need to do this within 30 days of moving to Oklahoma...
How to Buy Fuel Treatments
Adding a fuel additive to your gas tank when you fill up is one way to clean vital engine parts of deposits, improve the performance of your engine,...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...


Related questions

Q: My car shakes or vibrate at a stop

Hi there: Unfortunately, neither of those three error codes are associated with a component that is causing your vibration issue. The P0135 is related to the O2 sensor, and P0421 and P0401 are related to catalytic converter sensor issues. I...

Q: Po155cnf bank 2 sensor heater circuit P1620cnf Also code

The P0155 is the oxygen sensor located on the rear bank of cylinders and before the catalytic converter. Given your mileage, both oxygen sensors (pre-catalytic converter) should be replaced. The pre-cat sensors have the most affect on fuel mixture, saving...

Q: Venza 2010 L4-2.7L: My check engine light is permanently turned On. I have these codes P0012, P0016, P0017. What needs to be fixe

These are fault codes indicating problems related to the timing of your car's engine. Normally the car will not run very well or sometimes not at all when these are on. I would suggest having an expert from YourMechanic come...