Skip to main content

Make a Bosch Throttle Body Tester

Bosch throttle body for the Ferrari 360.

 If you've got a Bosch throttle body (series 280 750 ---) on your car, and it isn't a Ferrari 360, then it's likely if anything goes wrong, or is even suspected of being wrong with your throttle body, you'll just replace it. They're inexpensive, typically under $150, and super easy to install.

However, if you have a Ferrari 360 and suspect an issue with your throttle bodies (plural), then you're probably sweating right now. The stock of new OEM throttle bodies (aka holder) has been exhausted for years. There just aren't any more and there will likely never be any more produced. 

Used throttle bodies are generally useless, due to the requirement that both units be matched. Unmatched units, as in one degrading faster than the other, result in trouble codes and limp mode.

Luckily, the same exact innards to the 360's throttle bodies exist on quite a few other cars and these innards can be transplanted into the old 360 throttle body with excellent results.

The Ferrari 360 has some peculiar issues with the throttle body destroying one of the ECU's. These ECU's are no longer available and can be quite expensive to replace. The throttle bodies can destroy the ECU by drawing too much power and melting the H-bridge solder joints in the ECU. In theory, the ECU can be repaired but it's better to catch the problem before that happens and replace the throttle bodies. 

A test to determine how much power is being drawn by the throttle body would determine if it is a danger to the ECU and needs replacing. The total power that a Ferrari 360 ECU can supply before burning out is about six amps. A normal throttle body in good condition draws about one amp. So two, normally operating throttle bodies should draw about two amps. 

Testing a throttle body for amp draw is pretty easy once the details of how they work are laid out. The "280 750" series use two potentiometers to sense the position of the throttle plate and a motor with a PWM (Pulse Width Modulation) power source to move the throttle plate. 

This test is for the motor circuit only. The motor is typically the problem and can be tested using inexpensive parts and a simple setup.

Parts used in this test:

Onyehn PWM DC 10-60V Motor Speed Controller (~$13)
(note: any 12V motor speed controller that uses PWM is adequate)

DC Power supply (10-30V 10A) (~$100 - No longer available)
(Any similar power supply can be used or a 12V battery and clamp ammeter can be substituted)

Test lead banana to socket Pomona Electronics / 4771-36-2 / 4771-36-0 (red ~$12) (black ~$12)
(a male connector can be used too:

Instead of using a dedicated power supply, substitute a 12V battery and a clamp ammeter. A complete connector with pins can be purchased on eBay for less than $15 and can be used instead of the test leads. 

The rest of the parts are standard stuff available anywhere.

Here's the test setup.

The power supply is connected to the PWM controller. The positive (+) output is connected to pin #4 inside of the connector. The negative (ground) output is connected to pin #1. The pins are numbered inside the connector so it's easy to figure out which pins to use. A bit of light helps.

The test measures one thing precisely: the current required to open the throttle plate to full deflection. This is typically the peak power as the throttle body valve is being held closed by a rather strong spring. At full deflection, the spring is at maximum tension, so maximum current is needed to open it all the way.

Another data point is the position of the PWM motor controller knob. A PWM waveform is a square wave that is zero at 0% and high voltage, 12V in this case, at 100%. In between the wave consists of a zero portion and a high portion and the ratio of the two is the percentage.

This wikipedia image explains it nicely.

Since the PWM motor controller isn't "calibrated", we can only guess at what the numbers on the dial mean. A much more accurate way of measuring the duty cycle would be to use an oscilloscope. However, for the purpose of these tests, the knob is good enough.

The knob reading is really only good when testing two throttle bodies, as in the Ferrari 360. Since the two throttle bodies have to be matched to keep from throwing trouble codes, this test can show if there's a relative difference between the two units in regard to duty cycle.

Here's a video showing the test in action.

In the video, the motor controller knob is turned slowly until the throttle plate starts to move. From then on, the knob is turned very slowly since the range of power required to open it all the way should be fairly small. In this case, it was about 1/2 a "number" on the dial. 

One amp is about right for a good condition throttle body. The one in the test video is the Ferrari 360 model (280 750 038) rebuilt with parts from a Porsche model (280 750 474). If the amps are over two, that would concern me enough to rebuild the unit. The motor is completely replaceable using the parts from a Porsche unit.

This test doesn't address problems with the potentiometers. Testing those sensors would require a different and more elaborate test.

For a more indepth look at how a throttle body works and the pin layout, please see this article on the topic: Bosch Throttle Body Woes


Popular posts from this blog

Capote Elastic Bands Replacement

Virtually every Ferrari 360 and 430 has failing elastic bands in the capote, or soft top. The only cars that don't have these items failed right now have had them replaced in the last five years. My car is no exception and my original 20 year old elastic bands are well past the time they should be replaced. The top has a number of elastic bands that help control how it folds up and how things move. These bands are the same type of material as appears in underwear and stretch pants. As these things age, they wear out. So just like your old underwear, the elastic on the 360/430 top loses it's stretch. One of the things these elastic bands do is control a bar that shapes the headliner and roof line. This bar has to be pulled back and lie flat so the rest of the machinery that constitutes the top can fit into the tiny little space in the back of the car. When the elastic bands give out, the bar doesn't move to the right spot and the frame can impact on that bar as the top folds

Bosch Throttle Body (Holder) Woes

My 360 started going into limp mode a while back. It was subtle at first, with it starting to lose power after 4,000 RPM's and then less subtle when it would barely go above idle. Limp mode protects the car when some vital part has malfunctioned. I know a master Ferrari tech that is nice enough to answer questions for me about the car. He lives more than five hundred miles away and it's like telemedicine.  The codes indicated a problem in the drive-by-wire circuit, likely culprit: One or more TB's or the accelerator potentiometer (AP), which is the foot pedal sensor.  I had a good code reader that could monitor the AP voltages (2) and they appeared to be within specification. That left the TB's, one or both. After a long discussion with the tech, his answer was to replace the throttle bodies (TB). The Ferrari 360 has two TB's. One for each bank of four cylinders. To the Ferrari mentality, replacement could only be with two new TB's: "Ferrari likes replacing

Ferrari 360 Spider - One Year Ownership

 I'm coming up on the one year anniversary of owning my gated Ferrari 360 Spider. In that time, I've learned a tremendous amount about the car and especially, the systems. At this writing, the car is working 100%. I wish I could say that about the entire year. Unfortunately, with any twenty year old exotic, it's going to have good days and bad days. I've racked up about 1,200 miles in the year without being stranded. The car has had a few close calls but the car always carried me home. Thank you, sweet car, for that! Maintenance Issues I had an issue with the throttle bodies (TB) on the day I picked up the car. I just didn't know it. The TB issue would come and go as time passed, masquerading as other issues and finally, causing the engine to go into "pedal limp" (20% throttle). Eventually, the problem was properly diagnosed and cured.  Problems with the TB's can be cured very easily by simply replacing both affected units with new parts at a (parts al