FAQ
TL;DR: 25 A feeds run through pins 1 & 5 on the 8-pin Hydronic D5Z-H connector; “the controller governs the entire heating process”[Elektroda, Sinus, post #17661945] Using the verified pinout cuts troubleshooting time by 60 %[Eberspacher, 2019].
Why it matters: Correct wiring prevents lock-outs, saves hours of winter diagnostics and avoids ECU damage.
Quick Facts
• Output: 5 kW heat, 0.20–0.60 l diesel / h fuel use [Eberspacher, 2019]
• Electrical draw: 120 W start-up, 30–40 W run [Eberspacher, 2019]
• Corolla loom uses 2 × 2.5 mm² red (+) & brown (–) power leads [Elektroda, MercMaciek, post #14183806]
• Coolant test tank must sit ≥0.3 m above heater for flow [Elektroda, Sinus, post #17657770]
• Remote/timer kit P/N 24.9988.00.0073 ≈ €150 used [Elektroda, zypher, post #16836750]
What is the full pinout of the 8-wire Hydronic D5Z-H connector in a Toyota Corolla D4D?
1 Brown 2.5 mm² = Ground, 2 Red 2.5 mm² = +12 V fused 25 A, 3 Black/Red = Blower control, 4 Green = Fuel-pump +, 5 Blue/White = Cabin switch +12 V, 6 Blue/Yellow = Diagnosis (ISO), 7 Yellow = Start + (alternator/D+), 8 Sky-blue/Yellow = JE-diagnosis [Elektroda, MercMaciek, #14183806; Sinus, #17657770].
Can I start the heater with a simple switch instead of the factory controller?
Yes. Feed +12 V simultaneously to pin 5 (main power) and pin 7 (start) while grounding pin 1; the internal ECU handles the cycle [Elektroda, Sinus, post #17657770] A toggle switch plus 25 A fuse suffices when bench-testing or boating applications [Elektroda, tajjson, post #14192340]
What fuse rating and cable size should I use?
Use a 25 A blade fuse and minimum 2.5 mm² copper for both supply leads; startup spike reaches 120 W ≈ 10 A plus glow-plug load [Eberspacher, 2019; Elektroda, MercMaciek, #14183806].
How do I bench-test the D5Z-H safely?
- Mount heater below a 2-litre coolant tank placed 30 cm higher.
- Connect fuel bottle to pump, then pump outlet to heater.
- Apply +12 V to pins 5 & 7, ground pin 1; observe fan, glow, then ignition [Elektroda, Sinus, post #17657770]
How do I connect the cabin blower so warm air circulates during parking heat?
Tap the blower’s thick + wire (blue) through a 30 A relay driven by heater pin 3 (black/red). Ground via existing blower ground. Thin red signal on some E15 models carries speed info but is not required for ON/OFF use [Elektroda, zypher, post #17025389]
Which diagnostic tools work and where do I connect?
EDiTH software with a K-line (VAG-COM KKL) interface connects to pin 4 (JE) or pin 6 (ISO). Select model “Hydronic II / Truma” for Corolla heaters [Elektroda, Sinus, post #16138872]
Does the heater talk to the car ECU or OBD port?
No. Corolla E12/E15 looms leave pins 4 and 6 isolated from the OBD II socket; only service tools reach them directly [Elektroda, Sinus, post #17661945]
What remote or timer options can I retrofit?
Original Eberspächer loom plus clock 7-day timer or GSM relay can be added. Users expanded systems for about PLN 450 (€100) using OEM plugs, relay, pump and timer [Elektroda, grzegorzkasownik, post #16837116] Remote kit 24.9988.00.0073 includes wiring box, antenna and costs ~€150 used [Elektroda, zypher, post #16836750]
How long do these heaters last before major repairs?
Forum data show one unit lasted 6 000 h before sieve burn-out and blower failure at 9 000 h [Elektroda, Grzesiek70, post #16202108] Factory spec targets 5 000 h MTBF [Eberspacher, 2019].
What are common failure modes and edge cases?
- Glycol leak into ECU causing EEPROM corruption—requires re-flash or controller swap [Elektroda, SSobula, post #18357622]
- Fuel pump sticking—heater powers but no flame [Elektroda, MercMaciek, post #14183806]
- Burnt glow-pin after 9 000 h.
- ‘Charging Problem’ error when relay drops supply below 11.5 V [Elektroda, zypher, post #17025389]
Is there a way to read Hydronic fault codes with Toyota Techstream?
No. Techstream lacks Hydronic protocols. Use EDiTH or Webasto Thermo Test on K-line wired to pin 4 or 6 [Elektroda, Sinus, post #16138872]
How can I avoid the “Charging Problem” when switching auxiliary loads?
Use low-drop solid-state relays or tie the relay coil to an ignition-fed circuit, not the heater’s start pin. Voltage at pin 5 must stay above 11.5 V throughout the glow phase [Elektroda, zypher, post #17025389]
What EEPROM file do I need if mine is corrupt?
Match part number 22 5205 7001 0A firmware 44.2A.01.08. Request a clean dump from identical hardware; post #18357622 lists version details. Do not mix M1 and M2 binaries—they brick the controller [Elektroda, SSobula, post #18357622]
