[Linatros]

I have been trying to repair an extreme error on my BMW E90 since February.

It has multiple PT-can wiring failures, it does not communicate with the DDE (it appears in red in ISTA).

The errors it presents are:
It starts, and it works. On some occasions the control unit recognizes (it shows me an error on the oil sensor board), and the engine responds perfectly, with strength.
The air conditioning does not cool, except when it seems to recognize the DDE module.
RPM Meter and instant consumption meter do not work
Sometimes, despite not reading the DDE, the car does maintain its strength and accelerate correctly. When it fails, it is unable to accelerate, and cannot reach more than 80 km/h uphill.

These faults appear and disappear, it could be with some impact on the road, or simply after refueling, it is random

The budget from the official BMW company is impossible for me to assume, since they tell me that they must change components until it is resolved.

It has been through two other "electrical specialists", one of them could not give me any solution.

Another has changed the relay and its support by bridging a cable and changing the type of relay, which has not solved the problem. I have the relay and its original support, but I don't know the diagram, since I don't know how to read the ISTA D ones correctly. I check de fuses in DDE box and is OK.

I have cleaned each connector that I found visible with a special product, I have checked GND next to the DDE Box, and the GND connections next to the headlights.

I have replaced the battery with a 95AH AGM Varta, Coded and registered at a time when it was possible to communicate with the DDE.

Neither inpa, nor ISTA D, nor BimmerLink read the DDE. Sometimes appers in Green in Ista, and other appers in RED.

I have checked continuity between the connectors of the DDE Relay and the wiring that goes to it, also the Brown cable and they all have continuity. If I measure voltage, it shows 12V with the tester.

With Ista's ABL function to diagnose the DDE it shows me that the voltage is 0, that's why I don't understand what I'm overlooking.

I would appreciate any kind of help, or indication of where to look (within my abilities to understand diagrams) or any process I can check.

Thansk!
Sorry for my English, is so poor.

[gbalthrop]

Welcome to the Forum!
I understand your problem to be that the Engine ALWAYS starts & runs, but SOMETIMES you have normal power/performance, with NORMAL DDE PT-CAN Communication, but other times PT-CAN communication with JBE (Hub) is lost and the Engine continues to run, BUT at reduced Power.

If that is NOT the case, please clarify. Please answer the following questions & I will provide suggestions related to testing with ISTA/ INPA. I know NOTHING about your Diesel Engine, but can provide wiring & Test Help.

Questions:
1) Last-7 Characters of your VIN?
2) Warning Lights which appear on Instrument Cluster when Power Lost/ Limp Mode?
3) Do you have BOTH INPA & ISTA available?
4) Please attach "Control Unit Tree" as it appears when DDE is RED, and ALSO as it appears when DDE is Green in ISTA.
5) Please attach Fault Memory ScreenPrint showing ALL Faults in ALL Modules. We are particularly concerned with "Message Errors" where a Module reports NO Message from DDE.
6) When DDE is Green on Control Unit Tree, can you connect to DDE & view "Diagnosis Scan" Tab (view Live Data)?
7) Can you Connect to other Modules & view "Diagnosis Scan" Tab?
8) Was there any "Incident", or any work done on car PRIOR to February issue with DDE?

See attached pdf's related to ISTA use: 1) Fault Memory & Test Plan, & 2) ISTA as Shop Manual (Documents). With Answers to questions above, we can suggest "Next Steps". If Engine Runs/ Continues to Run, there is likely NO issue with Power Supply or Ground to DDE, but rather PT-CAN Bus communication issue.
George