Service Fix Kit - Check Engine Light
Bulletin: P91-001USSection: PRODUCT
Dated: 01/22/91
Applicable to: USA (except California) Canada
SUBJECT:
SERVICE-FIX KIT - "CHECK ENGINE" LIGHT - 1990/1991 MY
The "Check Engine" light is designed to inform the driver of an engine management problem which could adversely affect emissions.
It is possible that a fault code can be displayed and light illuminated where no fault exists.
An updated program for the ECU has been developed which will reduce the number of "false alarms" in the on-board diagnostic system. The improvement is "on-line" at the Factory and is now available as a Service-Fix.
The attached instructions include VIN ranges for applicable vehicles. However, a large number of vehicles have already been updated prior to delivery or through a special customer satisfaction action via our Technical Hotline. These vehicles should not exhibit any symptoms described in this bulletin.
This bulletin applies only to vehicles with the specific symptoms listed below.
SYMPTOMS
- Codes 12, 14, 17, 18, 19, 48, 68 or 69 displayed and no fault found with System
- Code 21
- A/C malfunction/cut-off at 65 mph.
ACTION
1. Replace the ECU or PROM in the existing ECU. See page 7 for ECU Identification. See pages 3 through 6 for work procedure.
Canadian Dealers: Replace ECU only.
2. Install serial link lead (if not present). See page 8.
3. Perform electrical/mechanical pre-checks. Check/adjust base idle using the Hand Held Tester and Base Idle Memory card. See pages 9 through 11.
Included with this Service Bulletin is the following package:
1. ECU exchange instructions
2. PROM exchange instructions (USA only)
3. ECU identification chart
4. Serial link lead instructions
5. Base idle checking/setting work procedure, including electrical/mechanical pre-checklist
6. Warranty information
7. Parts supply information
8. 2419 PROM (USA Only)
9. Base idle speed setting memory card for Hand Held Tester
10. "Green dot" I.D. stickers
No ECU is included. Please use the unit you received at the beginning of the H620 A/C Fix Action in August, 1990, as your "float". Remember that this "float" unit was provided at no charge and will ultimately be returned to RRNA. See E-Mail 19-91/01 if this or your other in-stock ECUs have not yet been upgraded to the latest specification.
This Service-Fix supersedes the H620 A/C Fix Program.
MISCELLANEOUS PARTS
Order Serial Link Leads, RTC7670 and Tamperproof Plugs, ETC6874 directly through the RRNA Parts Department.
ECU EXCHANGE INSTRUCTIONS
VINS:
...LA426808 - ...MA483126 (USA Only)
...LA391190 - ...MA600370 (Canada Only)
1. Remove seat base trim panels and ECU hold down screws.
2. Check multiple connector pins for condition/fit and connect new ECU - PRC9060R. Ignition must be off.
3. Start vehicle - observe that the "Check Engine" light goes out.
4. If O.K., place ECU in clip and secure to floor. CAUTION: THE CLIP IS SHARP EXERCISE CARE.
5. Replace trim panels.
6. Attach and complete both the buff colored tag shipped with new ECU and the normal yellow warranty tag to the removed unit before returning to Lucas.
NOTE:
Many 1990 model year vehicles are equipped with an external tune resistor located next to the ECU and connected with a blue 2-pin plug to the EFI harness. The updated ECU - PRC9060 contains an internal tune resistor. Remove and discard the existing resistor if equipped.
PROM EXCHANGE INSTRUCTIONS
VINS:
...LA391190 - ...LA426807
...MA483127 - ...MA600370
Tools Required:
Quantity Description
1 Posidriv screwdriver
1 Slip-joint pliers
1 TX20 torx screwdriver
*1 PROM removal tool
*1 Anti-static mat with grounding lead
*1 Ground cuff with lead
* Included with PROM Exchange Kit - RTC7680 - previously supplied to all Dealers at no charge for A/C Fix Program.
Before removing the ECU, do the following to check for normal operation of the ECU and related systems:
1. Switch on ignition and listen for the one (1) second fuel pump run.
2. Listen for ABS pump operation.
3. Switch off ignition.
WORK PROCEDURE
1. Remove the ECU from under the right front seat and disconnect multiple connector.
2. Place ECU on grounded anti-static mat, slip on anti-static wrist cuff and connect spiral jumper lead to mat. (Use longer jumper wire to ground mat to an electrical conduit or a cold water pipe).
3. Remove 4 TX20 torx screws from ECU and remove bottom half of cover.
4. Remove the printed circuit board from the case and place on anti-static mat.
5. Locate black PROM cover and remove by grasping with pliers across its width at one end or the other (avoid the center). A rocking motion aids removal. Set cover aside for later use.
6. Using the PROM removal tool, carefully lift the PROM from its socket. USE CARE NOT TO DAMAGE THE PRINTED CIRCUIT BOARD OR OTHER COMPONENTS. Store PROM in parts retention area with a completed Warranty Parts Tag.
7. Remove the new PROM (PRM2419) from its package and insert into the socket. NOTE: The half moon cut-out on the PROM faces away from the multiple connector and should align with a similar cut-out on the socket. Make sure all pins are engaged before pressing PROM fully in socket. (See illustration).
8. Snap PROM cover in place. If it doesn't fit, re-check PROM for correct installation.
9. Place Printed Circuit Board in case and reassemble cover. Make sure gasket is in place.
10. Attach the multiple connector to the ECU and perform the following initial checks:
A. Switch on ignition - the fuel pump should run for one (1) second. Listen for any unusual noises such as injectors operating or relays clicking which would indicate a problem.
B. Observe that the check engine light comes on and then extinguishes during the bulb check. If not, re-check the multiple connection and, if necessary, replace the ECU.
C. If the vehicle fails 'A' or 'B', re-check the multiple connector pins and socket. If this does not solve the problem, call the Technical Hotline at 1-800-562-5824.
QUALITY CHECK PROCEDURE
Start engine and observe the following:
1. The "Check Engine" light remains out.
2. Idle speed smoothness once stabilized.
3. Switch on the A/C and note idle speed compensation.
4. Rev the engine - no misfire should be noted.
5. Select drive and note idle speed compensation (brakes applied).
Replace the ECU if the vehicle fails any part of the above procedure.
otherwise:
6. Attach new label
7. Attach "Green dot" sticker
8. Install ECU and seat base trim panels.
ECU IDENTIFICATION
ECU's with Soldered in (Non-Replaceable) Prom:
^ Part No. - Factory Installed: PRC70B1
PRC8747
^ From VIN ...LA426808 to VIN ...MA483126
^ Date Code on ECU Label: 0590 to 4590
Example: Date Code 2590 = soldered in PROM
ECU's with Socketed (Replaceable) Prom:
^ Part No. - Factory Installed: PRC7081
PRC8747
^ From VIN ...LA391190 to VIN ...LA426807
From VIN ...MA483127 to VIN ...MA600370
^ Date Code (PRC7081): 0490 or below
Example: Date Code - 1289 = socketed PROM
^ Date Code Suffix Letter S (PRC8747): S indicates a socketed PROM on late VIN vehicles.
SERIAL LINK GROUNDING
Work Procedure
1990 Model Year
Up to VIN ...LA441247 If Not Done Previously
1. Locate the diagnostic socket (white) under the rear of the passenger front seat.
2. Locate the black/green wire (BG) on cap side of socket and cut the wire 2" from the socket. Strip 1/2" of insulation from the cut ends.
3. Slide the heat shrink tubing (supplied) over the 2" piece of wire from step 2. Join and solder the black connector lead (supplied) to the 2 BG wires. Shrink the insulating tubing over the joint with a heat gun.
4. Remove the orange lock bar and insert the female terminal on the black wire lead into the cap in the lower right hand position (viewed from the rear). Replace the lock bar and snap the cap onto the socket
Parts
1 each - Serial Link Modification Kit - Part No. RTC7670
CHECKING/SETTING BASE IDLE
Please read the attached Idle Speed Control information before proceeding.
Tools Required:
Range Rover Hand Held Tester (HHT)
Base Idle Memory Card P.N.: ENP1889 (version 1.0)
Timing Light
Smooth Jaw Hose Clamping Pliers or Equivalent Tool
3/16" Allen Wrench
Parts Required:
Tamperproof Plug P.N.: ETC6874
WORK PROCEDURE
Pre-Checks:
1. Updated ECU (PRC9060) or 2419 PROM installed in existing ECU.
2. Serial Link Lead (RTC7670) installed.
3. Visually check the following for fit/condition, repair as required.
A. All underhood vacuum hoses.
B. Air flow meter to plenum hose.
C. Throttle housing to stepper motor housing hose.
D. PCV hoses, filter and dipstick seal.
E. Stepper motor plug pins.
F. Any ignition faults
4. Check/clean PCV orifice in "T" piece. Check condition of ground leads/connections, especially at the rear of the left hand cylinder head. Tighten/clean/repair as required.
5. Check/set ignition timing at idle - Spec: 6° BTDC +/- 1°
CHECKING/SETTING PROCEDURE
1. Connect HHT with Base Idle Memory Card to serial link lead.
2. Start engine.
3. Prompt HHT until stepper motor display is shown on screen.
A. The engine must be warm and in Park or Neutral for the display to occur.
B. Disregard reference to Part No. PRC7081 shown on screen.
C. "F.S. Heater" = Heated windshield.
4. Test drive the vehicle for 1 to 2 miles to stabilize temperature - VERY IMPORTANT.
5. Immediately after the test drive, shut off the engine and wait until the main relay under the passenger seat "clicks" off. Switch off all accessories. The HHT display will indicate "Serial Link Failed" at this point. Disregard, since it will disappear on the next power up.
6. Restart the vehicle, hold the speed to 2,000 RPM for 30 seconds, then allow the engine to idle in Park.
7. Read the HHT display at idle. Spec. is 160 +/- 5 steps. If the position is in range, go to Step 9. If it is out of range, go to Step 8.
8. Remove the tamperproof plug and, with a 3/16" allen wrench, adjust the bypass screw. Opening (CCW) will increase the position number and vice versa. Shut off engine.
9. Repeat Steps 5, 6 and 7 as a check.
10. Steps 4-8 MUST be completed within a maximum of 10 minutes to ensure an accurate setting.If more than 10 minutes has elapsed, repeat Steps 3-8.
11. With the engine idling, clamp off the hose connecting the throttle housing to the stepper housing such that no air can flow through the hose. Note engine speed. If a stall occurs, repeat the procedure including the pre-checks. If the speed decreases slightly (to less than 600 RPM) proceed to Step 12.
12. Switch off the engine, allow the main relay to "click" off, remove the clamp and restart. Hold the engine at 2000 RPM for 30 seconds, then allow it to idle. Compare the stepper position with that previously checked/set. Repeat setting procedure if a change of greater than 10 steps is noted.
13. After removing HHT serial link harness, re-connect cap on serial link plug.
14. Install new Tamperproof Plug (if removed).
IDLE SPEED CONTROL - SYSTEM OPERATION
The Range Rover EFI System utilizes an idle speed motor (stepper motor) for automatic idle control. Acting on instructions from the ECU, the stepper motor rotates open or closed to compensate idle speed for:
Engine temperature
Engine condition
Altitude
A/C compressor load
Heated windshield load
Automatic transmission load
PCV system vacuum bleed
Alternator loading
Power steering load
From fully open to fully closed, the stepper motor's operation is divided into 180 positions or steps: 0 steps = fully open or retracted, 180 steps = fully closed or extended
The normal warm engine position depends upon engine condition, base idle setting, throttle position, lack of vacuum leaks, ignition timing and PCV system condition. As accessories are switched on and off, the stepper responds by opening and closing to compensate.
Turning the base idle screw opens or closes a small bypass passage in the plenum and alters the step position. With the engine at full operating temperature, timing correct, no accessory load, the transmission in park or neutral and purge not occurring, the correct setting position is 160 +/-5 steps. Over time, this value will change slightly as engine conditions change but the system is flexible enough to compensate - provided the initial setting is correct.
When the ignition is switched off (power down) the ECU automatically drives the stepper to the fully open, or 0, position. When the engine is re-started, the stepper closes (adds steps) in response to the ECU's need to maintain correct idle speed regardless of temperature, load, etc. In addition, the air conditioning, heated windshield and automatic transmission provide direct input to the ECU and program in a step change to compensate idle speed slightly. The automatic idle system operates only with the vehicle stopped or below 3 mph with the throttle fully closed, as indicated by an input from the road-speed transducer. Above 3 mph, the stepper motor is moved to a set position to prevent compensation while driving.
The on-board diagnostics in the ECU constantly compares step position to actual idle speed. If the ECU determines that the stepper is at either 0 or 180 and the idle speed is not within its control limits, the "check engine" light illuminates and a Code 48 is stored.
"CHECK ENGINE" LIGHT FIX - CLAIM INFORMATION
"CHECK ENGINE" LIGHT FIX - PARTS SUPPLY PROCESS