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Multec ECU malfunctions

By autotech-nic on March 26, 2016

We’re not sure if it’s a good or a bad sign, but almost every car connoisseur we speak to knows that many Vauxhalls are equipped with a Multec ECU. There’s an easy explanation for Vauxhall’s preference for Multec, rather than using a common Bosch ECU – General Motors and Multec-manufacturer Delco Electronics have been working together for decades. Delco Electronics was founded 1909 and became a well-known company in the late fifties thanks to its in-car stereo systems. Unfortunately, the company went bankrupt and switched owners several times. Partly because of all this, the ECU is now called Delphi Delco Multec HSFi-2.x.

AC2Why do so many people know the name ‘Multec’? Well, Multec ECUs are malfunctioning and this is due to several causes.

What’s causing the main malfunctions?

When using car-electronics it doesn’t matter where and how you use them, but always ensure protection against moisture, temperature fluctuations and vibration. Mounting an ECU right on top of the inlet manifold doesn’t provide the best possible environment. The ECU is operating in a hazardous environment full of vibrations and big differences in temperature. Several connections on the PCB (Printed Circuit Board) tend to tear or break so we always check all connections directly after every diagnosis. It’s rare to have all connections on the PCB in perfect order, almost every Multec sent in will undergo our full remanufacturing process.

The complaints we find on Multec ECUs are diverse, common issues include: Car doesn’t start, fuel pump isn’t activated; ignition fails on one or more cylinders; fluctuating RPM at idle; no throttle response; faults in EGR and no communication to the CAN-Bus.

Fault codes often accompany these complaints occur and will always start with ‘P0’ or ‘P1’ due to the Multec ECU causing a breakdown in the powertrain. A faulty ECU is specifically an engine problem, so the 3rd digit of the error code will always be a number between 1 and 5, the others relate to the gearbox or an optional hybrid drive. The following possibilities remain: P01XX, P02XX, P03XX, P04XX, P05XX, P11xx, P12xx, P13XX, P14xx, P15XX.

Our list of some of the most common error codes:
P0105: Manifold Absolute Pressure/Barometric Pressure – Circuit
P0230: Fuel Pump – Primary Circuit
P0335: Crank Shaft Sensor – No/Faulty Signal
P0340: Cam Shaft Sensor – No/Faulty Signal
P0351: t/m P0354 Ignition Coils 1 t/m 4
P1122: Accelerator Pedal Position Sensor 2
P1482: Fan Relay 2 – Electric Circuit Tiny Signal/Open
P1483: Fan Relay 3 – Electric Circuit Tiny Signal/Open
P1550: Electronic Throttle Control Reduced Power

3 Remanufacturing: the process

We can’t stress enough that ACtronics doesn’t repair defects, but remanufactures products. These ECU’s are very sensitive and we want to be absolutely sure a remanufactured ECU will have the quality equal to, or better than, the original. So, we not only repair all the complaints we encounter, but we also put each ECU through the complete remanufacturing process.

ACtronics remanufacturingWe begin by first removing the protective gel. Once all components are completely unprotected, we can remove all existing bonding wires. This is a very delicate process, but isn’t an issue thanks to our many years of experience. Once this second step is completed, all new bonding wires will be attached to the PCB using highly sophisticated equipment. The method we use is called ‘ultrasonic bonding’. The equipment is fully programmed and set up by our engineers and because of this we can also perform a ‘pull test’ on the freshly installed bonding wires. This ensures every new attachment is strong enough to withstand vibrations and fluctuations in temperatures. The newly made connections are even stronger than the original ones.

Once the bonding process is complete, it’s time for the final test – necessary to establish all the functions are working properly. An endurance test is then performed; raising the temperature in the ECU. After this, a special high specification gel is applied to protect the PCB and finally close the ECU with a new, self-developed cap.

If the ECU still isn’t working properly after these procedures, we will proceed using much more specific methods. There are many possibilities in the field of diagnosing and solving problems. In order to give you more insight into what may become defective, we will explain several components within the ECU in the next section…

The Multec HSFI-2.x in detail

2A Multec ECU is easily recognisable by its appearance. Two large 64-pin connectors, indicated by the letters “K” and “M”, connect both sides of the circuit board to the main harness. It’s also relatively simple to find out what every pin is used for. This makes diagnosing quite straightforward.

But it quickly becomes more complicated once we look into the ECU itself. The PCB consists of several layers and is completely filled with tiny components. These components are all used to support the main processor, which really needs more than just an EEPROM (Electrically Erasable Programmable Read-Only Memory) to operate correctly. But no worries, we’ll talk you through the main functions of the most important components.

Analogue to digital converters 

Sensors such as airflow meters and O2-sensors are designed to generate a variable voltage that depends on the measured value. An ECU doesn’t understand this variable value, because the processor is designed to process digital numbers. For that reason, converters are installed to convert these voltages into digital 10-bit values. 

Digital to analogue converters

Sometimes it’s necessary to have a digital value converted back to an analogue voltage. Certain actuators are able to vary the amount a valve will open and therefore an analogue input comes in handy. Digital to analogue converters ensure that these actuators can function properly.

Signal conditioners

Analogue values may come in different forms, but the converters always convert these values the same way into a digital number. They always use their own operating range of 0 to 5V. This could create some unusable values and therefore signal conditioners are installed onto the PCB. Simply put: the conditioners change all analogue values into a value that’s convenient for the converting process to execute correctly. The value of an O2 sensor, for example, varies between 0V and 1.1V but when a converter has an operating range between 0 and 5V, the degree of accuracy of the converted value won’t be ideal. In order to address this problem, the conditioner first increases the value 4 times. This way, the converter works with values between 0V and 4.4V, which are preferable. 

High-level digital output

ECU’s nowadays are used for actuating all kinds of devices and components. The Multec ECU, for example, actuates the cooling fan when necessary. These kinds of components often require a powerful input (relatively large Amps at 12V). But there’s one small problem; the delicate electronics in the ECU aren’t designed to cope with this. In order to solve this matter, a transistor (driver) is used. The transistor takes care of the powerful output that’s required to provide components with the right amount of power but sometimes even a transistor isn’t enough. The cooling fan requires such a large output that a transistor still won’t be strong enough. In that case, the output of the transistor is again used to actuate a relay.

Communication chips

These days cars are stuffed with all kinds of computers. The result of this broad network of components is multiple computers simultaneously trying to obtain the same signals at the same time. Therefore, it’s necessary for computers to communicate with each other. For example, if the ECU detects a fault, then it’s necessary for the engine check light to be lit up. To make this all possible, engineers created the Controller Area Network, or CAN-Bus. All received and transmitted CAN messages by the ECU are processed by a central communication chip. The chip decides whether a message is necessary for the ECU to use or not. So basically, this communication chip is the logistical centre of the ECU. Literally hundreds of messages each second are being processed. That’s also the main reason why the CAN network has to operate at speeds of up to 500 Kbps. 

Well, as you can see, there happens to be an awful lot within those seemingly simple Multec ECUs from Delphi Delco. Making the correct diagnosis isn’t easy at all. Fortunately, ACtronics specialists are fully conversant with all the secrets of the Multec ECU. If you ever encounter problems with this ECU, please contact us. We will look for a suitable solution.

Disassembly of the ECU

Mounting an ECU directly onto the manifold makes it very easy to disassemble. We recommend to always disconnect the battery before disassembly. Also keep your radio codes at hand.

The disassembly itself is very simple: Disconnect both connectors and loosen the four bolts on each corner. It really is that straightforward.

 If you have a defective ECU and want to see how ACtronics can help you, visit:







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