Hammer gurus- odd issue, please help
 

Hi All,

I just got a Bosch Hammer for my '90 C4. Everything works great- I can read all the installed modules/faults, direct drive all the drivable bits (fans, actuators, etc....) but I have one issue- the Hammer can not detect when the car is running. The upshot of this is that I can't get real-time output from the engine department sensors nor do an adaptation. To be clear- I can read the DME and activate the drivable bits (like the manifold tuning valve and the IAC valve) with no issue. Further, the car runs fine, maybe even great.

I have to assume that the RPM output is making it to the DME; again, the car runs fine and is entertainingly quick.

I also have to assume that the Hammer is working correctly. It will do everything I ask of it except the stuff that requires a running engine.

Consequently, I think the issue must be with the circuitry that communicates RPM to the diagnostic jack; either there's an issue with the output of the DME *or* an issue with the relay of same (have yet to check the wiring diagram; does the jack connect to the Central Informer?)

Any input on where to start troubleshooting is greatly appreciated!

TIA,
Robert

About the only thing you can do is to review the wiring diagram to see if there are any devices that may be defective between the Motronic signal output for rpm and the pin on the diagnostic plug.

I've done some further research and determined that I have a generic interface cable that only has 4 prongs vs. the factory ($800 !) 19 pin unit. John Speake of JDSPorsche fame answered an inquiry via email (immediately, I might add...) indicating that the Hammer needs to see a signal on the separate RPM signal line. He was also kind enough to tell me that the RPM pin (#14 on the car side) should be connected to Pin 1 on the Hammer end.

I'll mess about with it over the next few weeks and report back.