175 vs 173 ecu

[Creamchez]

Hello, new to the bmw community. I have a 91 318i and I’ve been trying to do the stomp test to check my engine codes. as I was looking at articles and other forums I saw that the stomp test works for some ecus like the 173, but I have a 175 and I haven’t been able to find any info on these. I’m basically wondering what the difference between the 173 and 175? And how can I check my codes without a code reader?


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[82eye]

the 173 was in the 6 cyl. the 175 was in the 4 cyl. i don't think they are interchangeable

[ForcedFirebird]

You still do the stomp test. If it doesn't work, the WOT part of your throttle switch is stuck open. Turn key, press accelerator 5x to the floor and the check engine light will blink the codes.

There aren't many codes that are worth looking up on theses ECU's. Pretty much the only time you'll get a code is when the sensor is completely absent.

175 ECU is Motronic 1.7, has coil on plug, and uses the later 88 pin connector. 173 is Motronic 1.3, uses a single coil and mid-year 55 pin connector.

[Creamchez]

You still do the stomp test. If it doesn't work, the WOT part of your throttle switch is stuck open. Turn key, press accelerator 5x to the floor and the check engine light will blink the codes.

There aren't many codes that are worth looking up on theses ECU's. Pretty much the only time you'll get a code is when the sensor is completely absent.

175 ECU is Motronic 1.7, has coil on plug, and uses the later 88 pin connector. 173 is Motronic 1.3, uses a single coil and mid-year 55 pin connector.

Yes, I've tried the whole stomp process and it doesn't work:/ Would replacing the tps fix this issue?


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[ForcedFirebird]

Test the TPS. You should have a short between the center and an outside pin when closed, all three pins open with any throttle input, then the center and opposing pin will be dead short.

The TPS is also adjustable. There's slots on the mounting screws, if it's not adjusted properly, then it won't see WOT, either.

You can "fake" the signal by turning the key and shorting the WOT pins 5x.

[bmwman91]

The M42 uses a potentiometer on the throttle, not a switch. Pull back the boot on the connector at the sensor and make sure that none of the 3 wires are broken at their terminals. If those pass the visual + light-tug test, then get a multimeter on them. The middle pin should show smoothly varying resistance relative to either of the outside pins as you open the throttle.

[ForcedFirebird]

Yes, I've tried the whole stomp process and it doesn't work:/ Would replacing the tps fix this issue?

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Try holding the pedal down on the last depression. Not sure why, but that works for me sometimes.

The M42 uses a potentiometer on the throttle.

UGH. Always forget that about the m42. I stand corrected. We rarely get m42's at work.